Task 003: .3G2 File Format
Task 003: .3G2 File Format
The .3G2 file format is a multimedia container format defined by the 3rd Generation Partnership Project 2 (3GPP2) for 3G CDMA2000 multimedia services. It is based on the ISO/IEC 14496-12 (MPEG-4 Part 12) base media file format and is optimized for mobile devices, offering reduced storage and bandwidth requirements compared to the related 3GP format. Below, I address each part of your request, providing a detailed response based on available information and addressing the complexities of handling .3G2 files programmatically.
1. Properties of the .3G2 File Format Intrinsic to Its File System
The .3G2 file format is a container format, meaning it encapsulates audio, video, and sometimes text (e.g., subtitles) streams. Its properties are defined by its structure as a multimedia container based on the ISO base media file format (MPEG-4 Part 12). The following are the intrinsic properties of the .3G2 file format relevant to its file system structure:
- File Extension:
.3g2,.3gp2, or.3gpp2 - MIME Type:
video/3gpp2,audio/3gpp2 - Uniform Type Identifier (UTI):
public.3gpp2 - Container Format: Based on ISO/IEC 14496-12 (MPEG-4 Part 12), which uses a box/atom structure to organize metadata and media data.
- Supported Video Codecs:
- MPEG-4 Part 2
- H.263
- MPEG-4 Part 10 (AVC/H.264)
- Supported Audio Codecs:
- AMR-NB (Adaptive Multi-Rate Narrowband)
- AMR-WB (Adaptive Multi-Rate Wideband)
- AAC-LC (Advanced Audio Coding Low Complexity)
- HE-AAC v1 (High-Efficiency AAC)
- EVRC (Enhanced Variable Rate Codec)
- EVRC-B
- EVRC-WB
- QCELP (Qualcomm Code Excited Linear Prediction, also known as 13K)
- SMV (Selectable Mode Vocoder)
- VMR-WB (Variable-Rate Multi-Mode Wideband)
- Text Support: Supports 3GPP Timed Text for subtitles or captions, with enhancements specific to 3GPP2.
- File Structure: Organized in a hierarchical box structure (atoms), including:
ftyp(File Type Box): Specifies the file type and compatibility (e.g.,3g2a,3g2b,3g2cfor different 3G2 versions).moov(Movie Box): Contains metadata about the media, such as duration, tracks, and codec information.mdat(Media Data Box): Stores the actual audio and video data.trak(Track Box): Defines individual tracks (video, audio, or text).mdia(Media Box): Contains media-specific information for each track.stbl(Sample Table Box): Describes sample timing and structure.- Other boxes like
mvhd(Movie Header),tkhd(Track Header), andudta(User Data). - Storage Efficiency: Designed to minimize storage and bandwidth usage, making it suitable for mobile devices.
- Interoperability: Optimized for CDMA-based mobile networks, with support for streaming and playback on 3G devices.
- File Size: Typically smaller than 3GP due to codec optimizations and compression tailored for CDMA networks.
- Metadata: Supports metadata for media description, such as title, artist, or creation date, stored in boxes like
udta.
These properties are derived from the 3GPP2 technical specification and related standards, ensuring compatibility with mobile devices and efficient data transmission.
2. Python Class for .3G2 File Handling
To handle .3G2 files in Python, we can use libraries like pymediainfo to extract metadata and ffmpeg-python for reading and writing media data. The class below opens a .3G2 file, decodes its properties, and allows writing a modified version (e.g., copying the file). Note that decoding the full box structure requires a library like mp4box or custom parsing, which is complex due to the binary nature of the format. For simplicity, this implementation focuses on extracting key properties using available libraries.
import pymediainfo
import ffmpeg
import os
class ThreeG2File:
def __init__(self, filepath):
self.filepath = filepath
self.properties = {}
def read_properties(self):
"""Read and decode .3G2 file properties."""
try:
media_info = pymediainfo.MediaInfo.parse(self.filepath)
for track in media_info.tracks:
if track.track_type == "General":
self.properties["file_extension"] = os.path.splitext(self.filepath)[1].lower()
self.properties["mime_type"] = track.internet_media_type or "video/3gpp2"
self.properties["file_size"] = track.file_size
self.properties["duration"] = track.duration / 1000 if track.duration else None
self.properties["format"] = track.format
elif track.track_type == "Video":
self.properties["video_codec"] = track.codec_id or track.format
self.properties["width"] = track.width
self.properties["height"] = track.height
self.properties["frame_rate"] = track.frame_rate
elif track.track_type == "Audio":
self.properties["audio_codec"] = track.codec_id or track.format
self.properties["sample_rate"] = track.sampling_rate
self.properties["channels"] = track.channel_s
elif track.track_type == "Text":
self.properties["text_format"] = track.format or "3GPP Timed Text"
except Exception as e:
print(f"Error reading properties: {e}")
def print_properties(self):
"""Print all properties to console."""
for key, value in self.properties.items():
print(f"{key}: {value}")
def write_file(self, output_filepath):
"""Write a copy of the .3G2 file."""
try:
stream = ffmpeg.input(self.filepath)
stream = ffmpeg.output(stream, output_filepath, c="copy")
ffmpeg.run(stream)
print(f"File written to {output_filepath}")
except ffmpeg.Error as e:
print(f"Error writing file: {e}")
# Example usage
if __name__ == "__main__":
file_path = "sample.3g2"
output_path = "output.3g2"
threeg2 = ThreeG2File(file_path)
threeg2.read_properties()
threeg2.print_properties()
threeg2.write_file(output_path)
Dependencies:
- Install
pymediainfo:pip install pymediainfo - Install
ffmpeg-python:pip install ffmpeg-python - Ensure FFmpeg is installed on your system (e.g., via
apt install ffmpegon Linux or downloading from the FFmpeg website).
Notes:
- The class uses
pymediainfoto extract metadata like file extension, MIME type, codecs, and track information. - The
write_filemethod creates a copy of the file using FFmpeg, preserving the original structure. - Full box parsing (e.g.,
ftyp,moov) requires a library likeisobmffor custom binary parsing, which is beyond the scope of this example due to complexity. - Error handling ensures robustness if the file is corrupted or unsupported.
3. Java Class for .3G2 File Handling
In Java, we can use the jaudiotagger library or a custom MP4 parser like mp4parser to handle .3G2 files, as they share the ISO base media file format. The following class uses mp4parser to parse the box structure and extract properties.
import com.coremedia.iso.IsoFile;
import com.coremedia.iso.boxes.*;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
public class ThreeG2File {
private String filepath;
private IsoFile isoFile;
private StringBuilder properties;
public ThreeG2File(String filepath) {
this.filepath = filepath;
this.properties = new StringBuilder();
}
public void readProperties() {
try {
isoFile = new IsoFile(filepath);
FileTypeBox ftyp = isoFile.getBoxes(FileTypeBox.class).get(0);
MovieBox moov = isoFile.getBoxes(MovieBox.class).get(0);
properties.append("file_extension: ").append(filepath.substring(filepath.lastIndexOf("."))).append("\n");
properties.append("mime_type: video/3gpp2\n");
properties.append("major_brand: ").append(ftyp.getMajorBrand()).append("\n");
for (TrackBox track : moov.getBoxes(TrackBox.class)) {
MediaBox mdia = track.getBoxes(MediaBox.class).get(0);
HandlerBox hdlr = mdia.getBoxes(HandlerBox.class).get(0);
String trackType = hdlr.getHandlerType();
if ("vide".equals(trackType)) {
SampleDescriptionBox stsd = mdia.getBoxes(MediaInformationBox.class).get(0)
.getBoxes(SampleTableBox.class).get(0)
.getBoxes(SampleDescriptionBox.class).get(0);
properties.append("video_codec: ").append(stsd.getSampleEntry().getType()).append("\n");
} else if ("soun".equals(trackType)) {
SampleDescriptionBox stsd = mdia.getBoxes(MediaInformationBox.class).get(0)
.getBoxes(SampleTableBox.class).get(0)
.getBoxes(SampleDescriptionBox.class).get(0);
properties.append("audio_codec: ").append(stsd.getSampleEntry().getType()).append("\n");
} else if ("text".equals(trackType)) {
properties.append("text_format: 3GPP Timed Text\n");
}
}
isoFile.close();
} catch (IOException e) {
System.err.println("Error reading properties: " + e.getMessage());
}
}
public void printProperties() {
System.out.println(properties.toString());
}
public void writeFile(String outputFilepath) {
try {
Files.copy(Paths.get(filepath), Paths.get(outputFilepath));
System.out.println("File written to " + outputFilepath);
} catch (IOException e) {
System.err.println("Error writing file: " + e.getMessage());
}
}
public static void main(String[] args) {
ThreeG2File threeG2 = new ThreeG2File("sample.3g2");
threeG2.readProperties();
threeG2.printProperties();
threeG2.writeFile("output.3g2");
}
}
Dependencies:
- Add
mp4parserto your project (e.g., via Maven):
<dependency>
<groupId>org.mp4parser</groupId>
<artifactId>isoparser</artifactId>
<version>1.9.41</version>
</dependency>
Notes:
- The
mp4parserlibrary parses the ISO base media file format, extracting boxes likeftypandmoov. - The class extracts key properties like file extension, MIME type, and codec types.
- Writing is implemented as a file copy for simplicity; modifying the box structure requires advanced manipulation with
mp4parser. - Error handling accounts for file access issues or invalid formats.
4. JavaScript Class for .3G2 File Handling
JavaScript lacks native support for parsing .3G2 files due to their binary structure, but we can use the mp4box.js library to parse the ISO base media file format in a browser or Node.js environment. The class below reads a .3G2 file and extracts its properties.
const MP4Box = require('mp4box');
class ThreeG2File {
constructor(filepath) {
this.filepath = filepath;
this.properties = {};
}
async readProperties() {
try {
const fs = require('fs');
const buffer = fs.readFileSync(this.filepath);
const mp4boxfile = MP4Box.createFile();
buffer.fileStart = 0;
mp4boxfile.appendBuffer(buffer);
return new Promise((resolve, reject) => {
mp4boxfile.onReady = (info) => {
this.properties.file_extension = this.filepath.split('.').pop().toLowerCase();
this.properties.mime_type = info.mime || 'video/3gpp2';
this.properties.major_brand = info.brands[0];
for (const track of info.tracks) {
if (track.type === 'video') {
this.properties.video_codec = track.codec;
} else if (track.type === 'audio') {
this.properties.audio_codec = track.codec;
} else if (track.type === 'text') {
this.properties.text_format = '3GPP Timed Text';
}
}
resolve();
};
mp4boxfile.onError = (e) => reject(e);
mp4boxfile.parse();
});
} catch (e) {
console.error('Error reading properties:', e);
}
}
printProperties() {
for (const [key, value] of Object.entries(this.properties)) {
console.log(`${key}: ${value}`);
}
}
writeFile(outputFilepath) {
try {
const fs = require('fs');
fs.copyFileSync(this.filepath, outputFilepath);
console.log(`File written to ${outputFilepath}`);
} catch (e) {
console.error('Error writing file:', e);
}
}
}
// Example usage
(async () => {
const threeG2 = new ThreeG2File('sample.3g2');
await threeG2.readProperties();
threeG2.printProperties();
threeG2.writeFile('output.3g2');
})();
Dependencies:
- Install
mp4box.js:npm install mp4box - Run in a Node.js environment, as file system access is required.
Notes:
mp4box.jsparses the ISO base media file format, suitable for .3G2 files.- The class extracts properties like file extension, MIME type, and codecs asynchronously.
- Writing is a simple file copy; modifying the file requires advanced buffer manipulation.
- Error handling ensures robustness for invalid or inaccessible files.
5. C Class for .3G2 File Handling
In C, parsing .3G2 files is complex due to the binary box structure. We can use the libavformat from FFmpeg to handle .3G2 files. The following C program reads and prints properties and copies the file.
#include <libavformat/avformat.h>
#include <stdio.h>
#include <string.h>
typedef struct {
char* filepath;
char* file_extension;
char* mime_type;
char* video_codec;
char* audio_codec;
char* text_format;
} ThreeG2File;
void threeg2file_init(ThreeG2File* file, const char* filepath) {
file->filepath = strdup(filepath);
file->file_extension = strrchr(filepath, '.') ? strdup(strrchr(filepath, '.') + 1) : "3g2";
file->mime_type = "video/3gpp2";
file->video_codec = NULL;
file->audio_codec = NULL;
file->text_format = NULL;
}
void threeg2file_read_properties(ThreeG2File* file) {
AVFormatContext* format_ctx = NULL;
if (avformat_open_input(&format_ctx, file->filepath, NULL, NULL) < 0) {
fprintf(stderr, "Error opening file\n");
return;
}
if (avformat_find_stream_info(format_ctx, NULL) < 0) {
fprintf(stderr, "Error finding stream info\n");
avformat_close_input(&format_ctx);
return;
}
for (unsigned int i = 0; i < format_ctx->nb_streams; i++) {
AVStream* stream = format_ctx->streams[i];
if (stream->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
file->video_codec = strdup(avcodec_get_name(stream->codecpar->codec_id));
} else if (stream->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
file->audio_codec = strdup(avcodec_get_name(stream->codecpar->codec_id));
} else if (stream->codecpar->codec_type == AVMEDIA_TYPE_SUBTITLE) {
file->text_format = "3GPP Timed Text";
}
}
avformat_close_input(&format_ctx);
}
void threeg2file_print_properties(ThreeG2File* file) {
printf("file_extension: %s\n", file->file_extension);
printf("mime_type: %s\n", file->mime_type);
if (file->video_codec) printf("video_codec: %s\n", file->video_codec);
if (file->audio_codec) printf("audio_codec: %s\n", file->audio_codec);
if (file->text_format) printf("text_format: %s\n", file->text_format);
}
void threeg2file_write_file(ThreeG2File* file, const char* output_filepath) {
FILE* src = fopen(file->filepath, "rb");
FILE* dst = fopen(output_filepath, "wb");
if (!src || !dst) {
fprintf(stderr, "Error opening files for copying\n");
if (src) fclose(src);
if (dst) fclose(dst);
return;
}
char buffer[4096];
size_t bytes;
while ((bytes = fread(buffer, 1, sizeof(buffer), src)) > 0) {
fwrite(buffer, 1, bytes, dst);
}
fclose(src);
fclose(dst);
printf("File written to %s\n", output_filepath);
}
void threeg2file_free(ThreeG2File* file) {
free(file->filepath);
free(file->file_extension);
free(file->mime_type);
if (file->video_codec) free(file->video_codec);
if (file->audio_codec) free(file->audio_codec);
if (file->text_format) free(file->text_format);
}
int main() {
ThreeG2File file;
threeg2file_init(&file, "sample.3g2");
threeg2file_read_properties(&file);
threeg2file_print_properties(&file);
threeg2file_write_file(&file, "output.3g2");
threeg2file_free(&file);
return 0;
}
Compilation:
- Compile with FFmpeg libraries:
gcc -o threeg2 threeg2.c -lavformat -lavcodec -lavutil - Ensure FFmpeg development libraries are installed (e.g.,
libavformat-devon Linux).
Notes:
- Uses
libavformatto parse the .3G2 file and extract codec information. - Writing is implemented as a file copy; modifying streams requires additional FFmpeg processing.
- Memory management ensures no leaks.
- Error handling covers file access and parsing issues.
General Notes and Limitations
- Parsing Complexity: The .3G2 format’s binary box structure (based on MPEG-4 Part 12) is complex to parse manually. Libraries like
mp4parser,mp4box.js, andlibavformatsimplify this but may not expose all boxes (e.g.,stbl,mdia) without custom extensions. - Writing Limitations: The provided classes perform a simple file copy for writing. Modifying .3G2 files (e.g., changing codecs or metadata) requires advanced manipulation of the box structure, which is library-specific and complex.
- Dependencies: Each implementation relies on external libraries due to the proprietary and binary nature of .3G2 files. Ensure these are installed and configured correctly.
- Testing: You’ll need a sample .3G2 file to test these classes. A sample can be downloaded from sources like docs.fileformat.com.
- Cross-Platform: The Python, Java, and JavaScript implementations are cross-platform, while the C implementation requires FFmpeg, which is widely supported but requires proper setup.
If you need more advanced functionality (e.g., modifying specific boxes or encoding new streams), please specify, and I can extend the implementations accordingly. For detailed .3G2 specifications, refer to the 3GPP2 technical specification (C.S0050-B v1.0).
1. List of Properties Intrinsic to the .3G2 File Format
Based on the .3G2 file format specifications (derived from 3GPP2 C.S0050 and the underlying ISO/IEC 14496-12 ISO base media file format), the intrinsic properties refer to the structural elements and fields within the file's box (atom) hierarchy. These are not filesystem attributes (like file size or permissions) but the internal data fields that define the container's metadata, tracks, and media characteristics. .3G2 files use a box-based structure where each box has a size (uint32), type (4-byte string), and content. The key boxes and their properties are listed below. I've focused on core, required, and common properties for .3G2 files, as the format supports variable extensions for codecs and media types.
File Type Box ('ftyp') Properties (required, identifies the file as .3G2):
- Major Brand (4-byte string, e.g., '3g2a', '3g2b', '3g2c')
- Minor Version (uint32)
- Compatible Brands (array of 4-byte strings, e.g., ['3g2a', 'isom'])
Movie Box ('moov') Properties (required, contains overall movie metadata):
- Movie Header Box ('mvhd') Properties:
- Version (uint8, typically 0)
- Flags (uint24, typically 0)
- Creation Time (uint32, seconds since 1904-01-01)
- Modification Time (uint32, seconds since 1904-01-01)
- Timescale (uint32, units per second)
- Duration (uint32, in timescale units)
- Rate (int32, fixed-point 16.16, typically 1<<16 for normal speed)
- Volume (int16, fixed-point 8.8, typically 1<<8 for full volume)
- Reserved (uint16 + uint32[2], typically 0)
- Matrix (int32[9], transformation matrix)
- Pre-defined (uint32[6], reserved, typically 0)
- Next Track ID (uint32)
Track Box ('trak') Properties (one per track, e.g., video, audio; optional but typically present):
Track Header Box ('tkhd') Properties:
- Version (uint8, typically 0)
- Flags (uint24, e.g., 0x000001 for enabled, 0x000002 for in-movie)
- Creation Time (uint32)
- Modification Time (uint32)
- Track ID (uint32)
- Reserved (uint32, 0)
- Duration (uint32)
- Reserved (uint32[2], 0)
- Layer (int16)
- Alternate Group (int16)
- Volume (int16, fixed-point 8.8)
- Reserved (uint16, 0)
- Matrix (int32[9])
- Width (uint32, fixed-point 16.16)
- Height (uint32, fixed-point 16.16)
Media Box ('mdia') Properties:
Media Header Box ('mdhd') Properties:
- Version (uint8)
- Flags (uint24)
- Creation Time (uint32)
- Modification Time (uint32)
- Timescale (uint32)
- Duration (uint32)
- Language (uint16, ISO-639-2/T code)
- Pre-defined (uint16, 0)
Handler Reference Box ('hdlr') Properties:
- Version (uint8, 0)
- Flags (uint24, 0)
- Pre-defined (uint32, 0)
- Handler Type (4-byte string, e.g., 'vide' for video, 'soun' for sound)
- Reserved (uint32[3], 0)
- Name (string, optional)
Media Information Box ('minf') Properties (contains sample table):
- Sample Table Box ('stbl') Properties:
- Sample Description Box ('stsd') Properties:
- Version (uint8, 0)
- Flags (uint24, 0)
- Entry Count (uint32)
- For each Sample Entry:
- Size (uint32)
- Format (4-byte string, e.g., 'mp4v' for MPEG-4 video, 'evrc' for EVRC audio, 'h263' for H.263)
- Reserved (uint8[6], 0)
- Data Reference Index (uint16)
- Codec-specific fields (variable, e.g., for video: version, revision, vendor, temporal quality, spatial quality, width, height, horiz resolution, vert resolution, data size, frame count, compressor name (32 bytes), depth, color table ID; for audio: channel count, sample size, compression ID, packet size, sample rate)
Other optional boxes (e.g., 'udta' for user data, 'meta' for metadata) may include properties like location ('gadi' box with week_number, seconds, GADSpecInfo) or encryption fields, but these are not always present. The media data itself is in 'mdat' box, but properties are metadata-focused.
2. Python Class for .3G2 Files
import struct
import os
class ThreeG2Handler:
def __init__(self, filepath):
self.filepath = filepath
self.properties = {}
self._parse()
def _read_box(self, f):
size = struct.unpack('>I', f.read(4))[0]
box_type = f.read(4).decode('utf-8')
return size, box_type
def _parse_ftyp(self, f, size):
self.properties['major_brand'] = f.read(4).decode('utf-8')
self.properties['minor_version'] = struct.unpack('>I', f.read(4))[0]
compatible_brands = []
remaining = size - 16 # header + major + minor
while remaining > 0:
compatible_brands.append(f.read(4).decode('utf-8'))
remaining -= 4
self.properties['compatible_brands'] = compatible_brands
def _parse_mvhd(self, f, size):
version = struct.unpack('>B', f.read(1))[0]
flags = struct.unpack('>3B', f.read(3))
self.properties['movie_creation_time'] = struct.unpack('>I', f.read(4))[0]
self.properties['movie_modification_time'] = struct.unpack('>I', f.read(4))[0]
self.properties['movie_timescale'] = struct.unpack('>I', f.read(4))[0]
self.properties['movie_duration'] = struct.unpack('>I', f.read(4))[0]
self.properties['rate'] = struct.unpack('>i', f.read(4))[0]
self.properties['volume'] = struct.unpack('>h', f.read(2))[0]
f.seek(10, 1) # reserved
self.properties['matrix'] = list(struct.unpack('>9i', f.read(36)))
f.seek(24, 1) # pre-defined
self.properties['next_track_id'] = struct.unpack('>I', f.read(4))[0]
def _parse_tkhd(self, f, size):
version = struct.unpack('>B', f.read(1))[0]
flags = struct.unpack('>3B', f.read(3))
self.properties.setdefault('tracks', []).append({})
track = self.properties['tracks'][-1]
track['creation_time'] = struct.unpack('>I', f.read(4))[0]
track['modification_time'] = struct.unpack('>I', f.read(4))[0]
track['track_id'] = struct.unpack('>I', f.read(4))[0]
f.seek(4, 1) # reserved
track['duration'] = struct.unpack('>I', f.read(4))[0]
f.seek(8, 1) # reserved
track['layer'] = struct.unpack('>h', f.read(2))[0]
track['alternate_group'] = struct.unpack('>h', f.read(2))[0]
track['volume'] = struct.unpack('>h', f.read(2))[0]
f.seek(2, 1) # reserved
track['matrix'] = list(struct.unpack('>9i', f.read(36)))
track['width'] = struct.unpack('>I', f.read(4))[0]
track['height'] = struct.unpack('>I', f.read(4))[0]
def _parse_mdhd(self, f, size):
version = struct.unpack('>B', f.read(1))[0]
flags = struct.unpack('>3B', f.read(3))
track = self.properties['tracks'][-1]
track['media_creation_time'] = struct.unpack('>I', f.read(4))[0]
track['media_modification_time'] = struct.unpack('>I', f.read(4))[0]
track['media_timescale'] = struct.unpack('>I', f.read(4))[0]
track['media_duration'] = struct.unpack('>I', f.read(4))[0]
language = struct.unpack('>H', f.read(2))[0]
track['language'] = chr(((language >> 10) & 0x1F) + 0x60) + chr(((language >> 5) & 0x1F) + 0x60) + chr((language & 0x1F) + 0x60)
f.seek(2, 1) # pre-defined
def _parse_hdlr(self, f, size):
version = struct.unpack('>B', f.read(1))[0]
flags = struct.unpack('>3B', f.read(3))
f.seek(4, 1) # pre-defined
track = self.properties['tracks'][-1]
track['handler_type'] = f.read(4).decode('utf-8')
f.seek(12, 1) # reserved
# Name is variable, skip for simplicity
def _parse_stsd(self, f, size):
version = struct.unpack('>B', f.read(1))[0]
flags = struct.unpack('>3B', f.read(3))
entry_count = struct.unpack('>I', f.read(4))[0]
track = self.properties['tracks'][-1]
track['sample_entries'] = []
for _ in range(entry_count):
entry_size = struct.unpack('>I', f.read(4))[0]
format_code = f.read(4).decode('utf-8')
f.seek(6, 1) # reserved
data_ref_index = struct.unpack('>H', f.read(2))[0]
# Codec-specific data (variable, parse based on format)
codec_data = f.read(entry_size - 16) # simplistic, store as bytes
track['sample_entries'].append({
'format': format_code,
'data_ref_index': data_ref_index,
'codec_data': codec_data
})
def _parse(self):
with open(self.filepath, 'rb') as f:
while True:
pos = f.tell()
if pos >= os.path.getsize(self.filepath):
break
size, box_type = self._read_box(f)
if box_type == 'ftyp':
self._parse_ftyp(f, size)
elif box_type == 'moov':
# Parse sub-boxes in moov
moov_end = pos + size
while f.tell() < moov_end:
sub_pos = f.tell()
sub_size, sub_type = self._read_box(f)
if sub_type == 'mvhd':
self._parse_mvhd(f, sub_size)
elif sub_type == 'trak':
# Parse sub-boxes in trak
trak_end = sub_pos + sub_size
while f.tell() < trak_end:
trak_sub_pos = f.tell()
trak_sub_size, trak_sub_type = self._read_box(f)
if trak_sub_type == 'tkhd':
self._parse_tkhd(f, trak_sub_size)
elif trak_sub_type == 'mdia':
mdia_end = trak_sub_pos + trak_sub_size
while f.tell() < mdia_end:
mdia_sub_pos = f.tell()
mdia_sub_size, mdia_sub_type = self._read_box(f)
if mdia_sub_type == 'mdhd':
self._parse_mdhd(f, mdia_sub_size)
elif mdia_sub_type == 'hdlr':
self._parse_hdlr(f, mdia_sub_size)
elif mdia_sub_type == 'minf':
minf_end = mdia_sub_pos + mdia_sub_size
while f.tell() < minf_end:
minf_sub_pos = f.tell()
minf_sub_size, minf_sub_type = self._read_box(f)
if minf_sub_type == 'stbl':
stbl_end = minf_sub_pos + minf_sub_size
while f.tell() < stbl_end:
stbl_sub_pos = f.tell()
stbl_sub_size, stbl_sub_type = self._read_box(f)
if stbl_sub_type == 'stsd':
self._parse_stsd(f, stbl_sub_size)
else:
f.seek(stbl_sub_size - 8, 1)
else:
f.seek(minf_sub_size - 8, 1)
else:
f.seek(mdia_sub_size - 8, 1)
else:
f.seek(trak_sub_size - 8, 1)
else:
f.seek(sub_size - 8, 1)
else:
f.seek(size - 8, 1)
def read_properties(self):
return self.properties
def write_properties(self, new_filepath=None):
if new_filepath is None:
new_filepath = self.filepath
# For writing, we'd need to reconstruct the entire file, but for simplicity, assume we modify properties and rewrite key boxes.
# This is a stub; full implementation would mirror parsing with packing.
with open(self.filepath, 'rb') as fin:
data = fin.read()
with open(new_filepath, 'wb') as fout:
fout.write(data) # Placeholder: actual write would pack structs with updated properties
print("Properties written (stub implementation).")
(Note: This Python class parses the file to read/decode properties into a dict. Writing is stubbed as full reconstruction is complex without a specific modification use case; it copies the file as-is. Codec-specific parsing is basic.)
3. Java Class for .3G2 Files
import java.io.RandomAccessFile;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class ThreeG2Handler {
private String filepath;
private Map<String, Object> properties = new HashMap<>();
public ThreeG2Handler(String filepath) {
this.filepath = filepath;
try {
parse();
} catch (IOException e) {
e.printStackTrace();
}
}
private int readInt(RandomAccessFile raf) throws IOException {
byte[] buf = new byte[4];
raf.readFully(buf);
return ByteBuffer.wrap(buf).order(ByteOrder.BIG_ENDIAN).getInt();
}
private short readShort(RandomAccessFile raf) throws IOException {
byte[] buf = new byte[2];
raf.readFully(buf);
return ByteBuffer.wrap(buf).order(ByteOrder.BIG_ENDIAN).getShort();
}
private String readString(RandomAccessFile raf, int length) throws IOException {
byte[] buf = new byte[length];
raf.readFully(buf);
return new String(buf, "UTF-8");
}
private void parse() throws IOException {
try (RandomAccessFile raf = new RandomAccessFile(filepath, "r")) {
while (raf.getFilePointer() < raf.length()) {
long pos = raf.getFilePointer();
int size = readInt(raf);
String boxType = readString(raf, 4);
if ("ftyp".equals(boxType)) {
parseFtyp(raf, size);
} else if ("moov".equals(boxType)) {
long moovEnd = pos + size;
while (raf.getFilePointer() < moovEnd) {
long subPos = raf.getFilePointer();
int subSize = readInt(raf);
String subType = readString(raf, 4);
if ("mvhd".equals(subType)) {
parseMvhd(raf, subSize);
} else if ("trak".equals(subType)) {
List<Map<String, Object>> tracks = (List<Map<String, Object>>) properties.computeIfAbsent("tracks", k -> new ArrayList<>());
Map<String, Object> track = new HashMap<>();
tracks.add(track);
long trakEnd = subPos + subSize;
while (raf.getFilePointer() < trakEnd) {
long trakSubPos = raf.getFilePointer();
int trakSubSize = readInt(raf);
String trakSubType = readString(raf, 4);
if ("tkhd".equals(trakSubType)) {
parseTkhd(raf, trakSubSize, track);
} else if ("mdia".equals(trakSubType)) {
long mdiaEnd = trakSubPos + trakSubSize;
while (raf.getFilePointer() < mdiaEnd) {
long mdiaSubPos = raf.getFilePointer();
int mdiaSubSize = readInt(raf);
String mdiaSubType = readString(raf, 4);
if ("mdhd".equals(mdiaSubType)) {
parseMdhd(raf, mdiaSubSize, track);
} else if ("hdlr".equals(mdiaSubType)) {
parseHdlr(raf, mdiaSubSize, track);
} else if ("minf".equals(mdiaSubType)) {
long minfEnd = mdiaSubPos + mdiaSubSize;
while (raf.getFilePointer() < minfEnd) {
long minfSubPos = raf.getFilePointer();
int minfSubSize = readInt(raf);
String minfSubType = readString(raf, 4);
if ("stbl".equals(minfSubType)) {
long stblEnd = minfSubPos + minfSubSize;
while (raf.getFilePointer() < stblEnd) {
long stblSubPos = raf.getFilePointer();
int stblSubSize = readInt(raf);
String stblSubType = readString(raf, 4);
if ("stsd".equals(stblSubType)) {
parseStsd(raf, stblSubSize, track);
} else {
raf.seek(stblSubPos + stblSubSize);
}
}
} else {
raf.seek(minfSubPos + minfSubSize);
}
}
} else {
raf.seek(mdiaSubPos + mdiaSubSize);
}
}
} else {
raf.seek(trakSubPos + trakSubSize);
}
}
} else {
raf.seek(subPos + subSize);
}
}
} else {
raf.seek(pos + size);
}
}
}
}
private void parseFtyp(RandomAccessFile raf, int size) throws IOException {
properties.put("major_brand", readString(raf, 4));
properties.put("minor_version", readInt(raf));
List<String> compatibleBrands = new ArrayList<>();
int remaining = size - 16;
while (remaining > 0) {
compatibleBrands.add(readString(raf, 4));
remaining -= 4;
}
properties.put("compatible_brands", compatibleBrands);
}
private void parseMvhd(RandomAccessFile raf, int size) throws IOException {
raf.skipBytes(1); // version
raf.skipBytes(3); // flags
properties.put("movie_creation_time", readInt(raf));
properties.put("movie_modification_time", readInt(raf));
properties.put("movie_timescale", readInt(raf));
properties.put("movie_duration", readInt(raf));
properties.put("rate", readInt(raf));
properties.put("volume", readShort(raf));
raf.skipBytes(10); // reserved
List<Integer> matrix = new ArrayList<>();
for (int i = 0; i < 9; i++) {
matrix.add(readInt(raf));
}
properties.put("matrix", matrix);
raf.skipBytes(24); // pre-defined
properties.put("next_track_id", readInt(raf));
}
private void parseTkhd(RandomAccessFile raf, int size, Map<String, Object> track) throws IOException {
raf.skipBytes(1); // version
raf.skipBytes(3); // flags
track.put("creation_time", readInt(raf));
track.put("modification_time", readInt(raf));
track.put("track_id", readInt(raf));
raf.skipBytes(4); // reserved
track.put("duration", readInt(raf));
raf.skipBytes(8); // reserved
track.put("layer", readShort(raf));
track.put("alternate_group", readShort(raf));
track.put("volume", readShort(raf));
raf.skipBytes(2); // reserved
List<Integer> matrix = new ArrayList<>();
for (int i = 0; i < 9; i++) {
matrix.add(readInt(raf));
}
track.put("matrix", matrix);
track.put("width", readInt(raf));
track.put("height", readInt(raf));
}
private void parseMdhd(RandomAccessFile raf, int size, Map<String, Object> track) throws IOException {
raf.skipBytes(1); // version
raf.skipBytes(3); // flags
track.put("media_creation_time", readInt(raf));
track.put("media_modification_time", readInt(raf));
track.put("media_timescale", readInt(raf));
track.put("media_duration", readInt(raf));
int languageCode = readShort(raf) & 0xFFFF;
String language = "" + (char) (((languageCode >> 10) & 0x1F) + 0x60) + (char) (((languageCode >> 5) & 0x1F) + 0x60) + (char) ((languageCode & 0x1F) + 0x60);
track.put("language", language);
raf.skipBytes(2); // pre-defined
}
private void parseHdlr(RandomAccessFile raf, int size, Map<String, Object> track) throws IOException {
raf.skipBytes(1); // version
raf.skipBytes(3); // flags
raf.skipBytes(4); // pre-defined
track.put("handler_type", readString(raf, 4));
raf.skipBytes(12); // reserved
// Skip name
}
private void parseStsd(RandomAccessFile raf, int size, Map<String, Object> track) throws IOException {
raf.skipBytes(1); // version
raf.skipBytes(3); // flags
int entryCount = readInt(raf);
List<Map<String, Object>> entries = new ArrayList<>();
for (int i = 0; i < entryCount; i++) {
int entrySize = readInt(raf);
String format = readString(raf, 4);
raf.skipBytes(6); // reserved
int dataRefIndex = readShort(raf) & 0xFFFF;
byte[] codecData = new byte[entrySize - 16];
raf.readFully(codecData);
Map<String, Object> entry = new HashMap<>();
entry.put("format", format);
entry.put("data_ref_index", dataRefIndex);
entry.put("codec_data", codecData);
entries.add(entry);
}
track.put("sample_entries", entries);
}
public Map<String, Object> readProperties() {
return properties;
}
public void writeProperties(String newFilepath) throws IOException {
// Stub: Copy file as-is; full write would involve rebuilding bytes with updated properties
try (RandomAccessFile in = new RandomAccessFile(filepath, "r");
RandomAccessFile out = new RandomAccessFile(newFilepath == null ? filepath : newFilepath, "rw")) {
byte[] buffer = new byte[1024];
int len;
while ((len = in.read(buffer)) != -1) {
out.write(buffer, 0, len);
}
}
System.out.println("Properties written (stub implementation).");
}
}
(Note: Similar to Python, this reads/decodes properties. Writing is stubbed.)
4. JavaScript Class for .3G2 Files (Node.js)
const fs = require('fs');
class ThreeG2Handler {
constructor(filepath) {
this.filepath = filepath;
this.properties = {};
this.parse();
}
parse() {
const buffer = fs.readFileSync(this.filepath);
let offset = 0;
while (offset < buffer.length) {
const size = buffer.readUInt32BE(offset);
const boxType = buffer.toString('utf8', offset + 4, offset + 8);
offset += 8;
if (boxType === 'ftyp') {
this.parseFtyp(buffer, offset, size);
} else if (boxType === 'moov') {
const moovEnd = offset - 8 + size;
while (offset < moovEnd) {
const subSize = buffer.readUInt32BE(offset);
const subType = buffer.toString('utf8', offset + 4, offset + 8);
offset += 8;
if (subType === 'mvhd') {
this.parseMvhd(buffer, offset, subSize);
} else if (subType === 'trak') {
if (!this.properties.tracks) this.properties.tracks = [];
const track = {};
this.properties.tracks.push(track);
const trakEnd = offset - 8 + subSize;
while (offset < trakEnd) {
const trakSubSize = buffer.readUInt32BE(offset);
const trakSubType = buffer.toString('utf8', offset + 4, offset + 8);
offset += 8;
if (trakSubType === 'tkhd') {
this.parseTkhd(buffer, offset, trakSubSize, track);
} else if (trakSubType === 'mdia') {
const mdiaEnd = offset - 8 + trakSubSize;
while (offset < mdiaEnd) {
const mdiaSubSize = buffer.readUInt32BE(offset);
const mdiaSubType = buffer.toString('utf8', offset + 4, offset + 8);
offset += 8;
if (mdiaSubType === 'mdhd') {
this.parseMdhd(buffer, offset, mdiaSubSize, track);
} else if (mdiaSubType === 'hdlr') {
this.parseHdlr(buffer, offset, mdiaSubSize, track);
} else if (mdiaSubType === 'minf') {
const minfEnd = offset - 8 + mdiaSubSize;
while (offset < minfEnd) {
const minfSubSize = buffer.readUInt32BE(offset);
const minfSubType = buffer.toString('utf8', offset + 4, offset + 8);
offset += 8;
if (minfSubType === 'stbl') {
const stblEnd = offset - 8 + minfSubSize;
while (offset < stblEnd) {
const stblSubSize = buffer.readUInt32BE(offset);
const stblSubType = buffer.toString('utf8', offset + 4, offset + 8);
offset += 8;
if (stblSubType === 'stsd') {
this.parseStsd(buffer, offset, stblSubSize, track);
} else {
offset += stblSubSize - 8;
}
}
} else {
offset += minfSubSize - 8;
}
}
} else {
offset += mdiaSubSize - 8;
}
}
} else {
offset += trakSubSize - 8;
}
}
} else {
offset += subSize - 8;
}
}
} else {
offset += size - 8;
}
}
}
parseFtyp(buffer, offset, size) {
this.properties.major_brand = buffer.toString('utf8', offset, offset + 4);
offset += 4;
this.properties.minor_version = buffer.readUInt32BE(offset);
offset += 4;
this.properties.compatible_brands = [];
let remaining = size - 16;
while (remaining > 0) {
this.properties.compatible_brands.push(buffer.toString('utf8', offset, offset + 4));
offset += 4;
remaining -= 4;
}
}
parseMvhd(buffer, offset, size) {
offset += 1; // version
offset += 3; // flags
this.properties.movie_creation_time = buffer.readUInt32BE(offset);
offset += 4;
this.properties.movie_modification_time = buffer.readUInt32BE(offset);
offset += 4;
this.properties.movie_timescale = buffer.readUInt32BE(offset);
offset += 4;
this.properties.movie_duration = buffer.readUInt32BE(offset);
offset += 4;
this.properties.rate = buffer.readInt32BE(offset);
offset += 4;
this.properties.volume = buffer.readInt16BE(offset);
offset += 2;
offset += 10; // reserved
this.properties.matrix = [];
for (let i = 0; i < 9; i++) {
this.properties.matrix.push(buffer.readInt32BE(offset));
offset += 4;
}
offset += 24; // pre-defined
this.properties.next_track_id = buffer.readUInt32BE(offset);
}
parseTkhd(buffer, offset, size, track) {
offset += 1; // version
offset += 3; // flags
track.creation_time = buffer.readUInt32BE(offset);
offset += 4;
track.modification_time = buffer.readUInt32BE(offset);
offset += 4;
track.track_id = buffer.readUInt32BE(offset);
offset += 4;
offset += 4; // reserved
track.duration = buffer.readUInt32BE(offset);
offset += 4;
offset += 8; // reserved
track.layer = buffer.readInt16BE(offset);
offset += 2;
track.alternate_group = buffer.readInt16BE(offset);
offset += 2;
track.volume = buffer.readInt16BE(offset);
offset += 2;
offset += 2; // reserved
track.matrix = [];
for (let i = 0; i < 9; i++) {
track.matrix.push(buffer.readInt32BE(offset));
offset += 4;
}
track.width = buffer.readUInt32BE(offset);
offset += 4;
track.height = buffer.readUInt32BE(offset);
}
parseMdhd(buffer, offset, size, track) {
offset += 1; // version
offset += 3; // flags
track.media_creation_time = buffer.readUInt32BE(offset);
offset += 4;
track.media_modification_time = buffer.readUInt32BE(offset);
offset += 4;
track.media_timescale = buffer.readUInt32BE(offset);
offset += 4;
track.media_duration = buffer.readUInt32BE(offset);
offset += 4;
const langCode = buffer.readUInt16BE(offset);
track.language = String.fromCharCode(((langCode >> 10) & 0x1F) + 0x60) + String.fromCharCode(((langCode >> 5) & 0x1F) + 0x60) + String.fromCharCode((langCode & 0x1F) + 0x60);
offset += 2;
offset += 2; // pre-defined
}
parseHdlr(buffer, offset, size, track) {
offset += 1; // version
offset += 3; // flags
offset += 4; // pre-defined
track.handler_type = buffer.toString('utf8', offset, offset + 4);
offset += 4;
offset += 12; // reserved
// Skip name
}
parseStsd(buffer, offset, size, track) {
offset += 1; // version
offset += 3; // flags
const entryCount = buffer.readUInt32BE(offset);
offset += 4;
track.sample_entries = [];
for (let i = 0; i < entryCount; i++) {
const entrySize = buffer.readUInt32BE(offset);
offset += 4;
const format = buffer.toString('utf8', offset, offset + 4);
offset += 4;
offset += 6; // reserved
const dataRefIndex = buffer.readUInt16BE(offset);
offset += 2;
const codecData = buffer.slice(offset, offset + entrySize - 16);
offset += entrySize - 16;
track.sample_entries.push({
format,
data_ref_index: dataRefIndex,
codec_data: codecData
});
}
}
readProperties() {
return this.properties;
}
writeProperties(newFilepath = null) {
if (!newFilepath) newFilepath = this.filepath;
fs.copyFileSync(this.filepath, newFilepath);
console.log('Properties written (stub implementation).');
}
}
(Note: Uses Node.js fs for file I/O. Parsing is buffer-based. Writing stubbed.)
5. C++ Class for .3G2 Files
#include <fstream>
#include <iostream>
#include <vector>
#include <map>
#include <string>
#include <cstring>
#include <cstdint>
class ThreeG2Handler {
private:
std::string filepath;
std::map<std::string, std::any> properties; // Use std::any for flexibility (C++17)
uint32_t readUInt32(std::ifstream& ifs) {
uint32_t val;
ifs.read(reinterpret_cast<char*>(&val), 4);
val = __builtin_bswap32(val); // Big-endian
return val;
}
int32_t readInt32(std::ifstream& ifs) {
int32_t val;
ifs.read(reinterpret_cast<char*>(&val), 4);
val = __builtin_bswap32(val);
return val;
}
uint16_t readUInt16(std::ifstream& ifs) {
uint16_t val;
ifs.read(reinterpret_cast<char*>(&val), 2);
val = __builtin_bswap16(val);
return val;
}
int16_t readInt16(std::ifstream& ifs) {
int16_t val;
ifs.read(reinterpret_cast<char*>(&val), 2);
val = __builtin_bswap16(val);
return val;
}
std::string readString(std::ifstream& ifs, size_t length) {
std::string str(length, '\0');
ifs.read(&str[0], length);
return str;
}
void parse() {
std::ifstream ifs(filepath, std::ios::binary);
if (!ifs) return;
while (ifs) {
std::streampos pos = ifs.tellg();
uint32_t size = readUInt32(ifs);
std::string boxType = readString(ifs, 4);
if (boxType == "ftyp") {
parseFtyp(ifs, size);
} else if (boxType == "moov") {
std::streampos moovEnd = pos + static_cast<std::streamoff>(size);
while (ifs.tellg() < moovEnd) {
std::streampos subPos = ifs.tellg();
uint32_t subSize = readUInt32(ifs);
std::string subType = readString(ifs, 4);
if (subType == "mvhd") {
parseMvhd(ifs, subSize);
} else if (subType == "trak") {
auto& tracks = std::any_cast<std::vector<std::map<std::string, std::any>>&>(properties["tracks"] = std::vector<std::map<std::string, std::any>>{});
std::map<std::string, std::any> track;
tracks.push_back(track);
std::streampos trakEnd = subPos + static_cast<std::streamoff>(subSize);
while (ifs.tellg() < trakEnd) {
std::streampos trakSubPos = ifs.tellg();
uint32_t trakSubSize = readUInt32(ifs);
std::string trakSubType = readString(ifs, 4);
if (trakSubType == "tkhd") {
parseTkhd(ifs, trakSubSize, tracks.back());
} else if (trakSubType == "mdia") {
std::streampos mdiaEnd = trakSubPos + static_cast<std::streamoff>(trakSubSize);
while (ifs.tellg() < mdiaEnd) {
std::streampos mdiaSubPos = ifs.tellg();
uint32_t mdiaSubSize = readUInt32(ifs);
std::string mdiaSubType = readString(ifs, 4);
if (mdiaSubType == "mdhd") {
parseMdhd(ifs, mdiaSubSize, tracks.back());
} else if (mdiaSubType == "hdlr") {
parseHdlr(ifs, mdiaSubSize, tracks.back());
} else if (mdiaSubType == "minf") {
std::streampos minfEnd = mdiaSubPos + static_cast<std::streamoff>(mdiaSubSize);
while (ifs.tellg() < minfEnd) {
std::streampos minfSubPos = ifs.tellg();
uint32_t minfSubSize = readUInt32(ifs);
std::string minfSubType = readString(ifs, 4);
if (minfSubType == "stbl") {
std::streampos stblEnd = minfSubPos + static_cast<std::streamoff>(minfSubSize);
while (ifs.tellg() < stblEnd) {
std::streampos stblSubPos = ifs.tellg();
uint32_t stblSubSize = readUInt32(ifs);
std::string stblSubType = readString(ifs, 4);
if (stblSubType == "stsd") {
parseStsd(ifs, stblSubSize, tracks.back());
} else {
ifs.seekg(stblSubSize - 8, std::ios::cur);
}
}
} else {
ifs.seekg(minfSubSize - 8, std::ios::cur);
}
}
} else {
ifs.seekg(mdiaSubSize - 8, std::ios::cur);
}
}
} else {
ifs.seekg(trakSubSize - 8, std::ios::cur);
}
}
} else {
ifs.seekg(subSize - 8, std::ios::cur);
}
}
} else {
ifs.seekg(size - 8, std::ios::cur);
}
}
}
void parseFtyp(std::ifstream& ifs, uint32_t size) {
properties["major_brand"] = readString(ifs, 4);
properties["minor_version"] = readUInt32(ifs);
std::vector<std::string> compatibleBrands;
uint32_t remaining = size - 16;
while (remaining > 0) {
compatibleBrands.push_back(readString(ifs, 4));
remaining -= 4;
}
properties["compatible_brands"] = compatibleBrands;
}
void parseMvhd(std::ifstream& ifs, uint32_t size) {
ifs.seekg(1, std::ios::cur); // version
ifs.seekg(3, std::ios::cur); // flags
properties["movie_creation_time"] = readUInt32(ifs);
properties["movie_modification_time"] = readUInt32(ifs);
properties["movie_timescale"] = readUInt32(ifs);
properties["movie_duration"] = readUInt32(ifs);
properties["rate"] = readInt32(ifs);
properties["volume"] = readInt16(ifs);
ifs.seekg(10, std::ios::cur); // reserved
std::vector<int32_t> matrix(9);
for (auto& val : matrix) val = readInt32(ifs);
properties["matrix"] = matrix;
ifs.seekg(24, std::ios::cur); // pre-defined
properties["next_track_id"] = readUInt32(ifs);
}
void parseTkhd(std::ifstream& ifs, uint32_t size, std::map<std::string, std::any>& track) {
ifs.seekg(1, std::ios::cur); // version
ifs.seekg(3, std::ios::cur); // flags
track["creation_time"] = readUInt32(ifs);
track["modification_time"] = readUInt32(ifs);
track["track_id"] = readUInt32(ifs);
ifs.seekg(4, std::ios::cur); // reserved
track["duration"] = readUInt32(ifs);
ifs.seekg(8, std::ios::cur); // reserved
track["layer"] = readInt16(ifs);
track["alternate_group"] = readInt16(ifs);
track["volume"] = readInt16(ifs);
ifs.seekg(2, std::ios::cur); // reserved
std::vector<int32_t> matrix(9);
for (auto& val : matrix) val = readInt32(ifs);
track["matrix"] = matrix;
track["width"] = readUInt32(ifs);
track["height"] = readUInt32(ifs);
}
void parseMdhd(std::ifstream& ifs, uint32_t size, std::map<std::string, std::any>& track) {
ifs.seekg(1, std::ios::cur); // version
ifs.seekg(3, std::ios::cur); // flags
track["media_creation_time"] = readUInt32(ifs);
track["media_modification_time"] = readUInt32(ifs);
track["media_timescale"] = readUInt32(ifs);
track["media_duration"] = readUInt32(ifs);
uint16_t langCode = readUInt16(ifs);
std::string language(3, '\0');
language[0] = ((langCode >> 10) & 0x1F) + 0x60;
language[1] = ((langCode >> 5) & 0x1F) + 0x60;
language[2] = (langCode & 0x1F) + 0x60;
track["language"] = language;
ifs.seekg(2, std::ios::cur); // pre-defined
}
void parseHdlr(std::ifstream& ifs, uint32_t size, std::map<std::string, std::any>& track) {
ifs.seekg(1, std::ios::cur); // version
ifs.seekg(3, std::ios::cur); // flags
ifs.seekg(4, std::ios::cur); // pre-defined
track["handler_type"] = readString(ifs, 4);
ifs.seekg(12, std::ios::cur); // reserved
// Skip name
}
void parseStsd(std::ifstream& ifs, uint32_t size, std::map<std::string, std::any>& track) {
ifs.seekg(1, std::ios::cur); // version
ifs.seekg(3, std::ios::cur); // flags
uint32_t entryCount = readUInt32(ifs);
std::vector<std::map<std::string, std::any>> entries;
for (uint32_t i = 0; i < entryCount; ++i) {
uint32_t entrySize = readUInt32(ifs);
std::string format = readString(ifs, 4);
ifs.seekg(6, std::ios::cur); // reserved
uint16_t dataRefIndex = readUInt16(ifs);
std::vector<char> codecData(entrySize - 16);
ifs.read(codecData.data(), entrySize - 16);
std::map<std::string, std::any> entry;
entry["format"] = format;
entry["data_ref_index"] = dataRefIndex;
entry["codec_data"] = codecData;
entries.push_back(entry);
}
track["sample_entries"] = entries;
}
public:
ThreeG2Handler(const std::string& fp) : filepath(fp) {
parse();
}
// Read properties (simplified, print or return map)
void readProperties() {
// For demonstration, print to cout
std::cout << "Properties: " << std::endl;
// Implement printing logic as needed
}
void writeProperties(const std::string& newFilepath = "") {
std::string outPath = newFilepath.empty() ? filepath : newFilepath;
std::ifstream in(filepath, std::ios::binary);
std::ofstream out(outPath, std::ios::binary);
out << in.rdbuf();
std::cout << "Properties written (stub implementation)." << std::endl;
}
};
(Note: Uses C++17 std::any for property storage. Parsing is stream-based. Writing stubbed. Compile with -std=c++17.)