AVC / H.264 Annex B Encoder (Run)
Contents
AVC / H.264 Annex B Encoder (Run)#
This article explains how you can use Transcoder::run to encode a raw YUV video file to AVC / H.264 Annex B elementary stream format.
The code snippets in this article are from the enc_avc_file macOS sample.
Source Video#
For source we use the foreman_qcif.yuv file from the AVBlocks Assets repository. After downloading and unzipping you will find foreman_qcif.yuv in the vid subdirectory.
Code#
This code takes a raw YUV video file and encodes it to compressed H.264 Annex B format.
Initialize AVBlocks#
The first step in any AVBlocks application is to initialize the library. This must be done before using any other AVBlocks functionality. The Library::initialize() method sets up the internal state and loads necessary codecs. Always remember to call Library::shutdown() at the end of your program to properly clean up resources and release any allocated memory.
int main(int argc, char* argv[])
{
Options opt;
switch(prepareOptions(opt, argc, argv))
{
case Command: return 0;
case Error: return 1;
case Parsed: break;
}
Library::initialize();
bool encodeResult = encode(opt);
Library::shutdown();
return encodeResult ? 0 : 1;
}
Configure Input Socket#
The input socket defines the source raw YUV video data. We need to specify the video parameters including frame dimensions, frame rate, color format, and scan type. These parameters must match the actual properties of the input YUV file. In this example, we’re reading QCIF resolution (176x144) YUV 4:2:0 progressive video at 30 frames per second.
primo::ref<MediaSocket> createInputSocket(Options& opt)
{
auto socket = primo::make_ref(Library::createMediaSocket());
socket->setStreamType(StreamType::UncompressedVideo);
socket->setFile(primo::ustring(opt.yuv_file));
auto pin = primo::make_ref(Library::createMediaPin());
socket->pins()->add(pin.get());
auto vsi = primo::make_ref(Library::createVideoStreamInfo());
pin->setStreamInfo(vsi.get());
vsi->setStreamType(StreamType::UncompressedVideo);
vsi->setFrameWidth(opt.frame_size.width_);
vsi->setFrameHeight(opt.frame_size.height_);
vsi->setColorFormat(opt.yuv_color.Id);
vsi->setFrameRate(opt.fps);
vsi->setScanType(ScanType::Progressive);
return socket;
}
Configure Output Socket#
The output socket defines where and how the encoded H.264 video data will be written. We configure it to output an H.264 Annex B elementary stream file. The socket represents the output destination, while the pin represents the specific video stream within that destination. By setting StreamSubType::AVC_Annex_B, we ensure the output uses the Annex B format with start codes, which is suitable for elementary streams and broadcasting applications.
primo::ref<MediaSocket> createOutputSocket(Options& opt)
{
auto socket = primo::make_ref(Library::createMediaSocket());
socket->setFile(primo::ustring(opt.h264_file));
socket->setStreamType(StreamType::H264);
auto pin = primo::make_ref(Library::createMediaPin());
socket->pins()->add(pin.get());
auto vsi = primo::make_ref(Library::createVideoStreamInfo());
pin->setStreamInfo(vsi.get());
vsi->setStreamType(StreamType::H264);
vsi->setStreamSubType(StreamSubType::AVC_Annex_B);
return socket;
}
Configure Transcoder and Encode#
This is the main encoding function that ties everything together. First, we create an input socket that points to the YUV file we want to encode. Then we create the output socket using our helper function. The transcoder is the core component that performs the actual encoding - it takes the uncompressed YUV data from the input and converts it to compressed H.264 data for the output.
The setAllowDemoMode(true) call allows the transcoder to work even without a valid license (useful for testing, but not recommended for production). We then add our input and output sockets to the transcoder, open it to prepare for processing, run the actual transcoding operation, and finally close it to clean up.
bool encode(Options& opt)
{
// create input socket
auto inSocket = createInputSocket(opt);
// create output socket
auto outSocket = createOutputSocket(opt);
// create transcoder
auto transcoder = primo::make_ref(Library::createTranscoder());
transcoder->setAllowDemoMode(true);
transcoder->inputs()->add(inSocket.get());
transcoder->outputs()->add(outSocket.get());
// transcoder will fail if output exists (by design)
deleteFile(primo::ustring(opt.h264_file));
cout << "Transcoder open: ";
if(transcoder->open())
{
printStatus(transcoder->error());
if(!transcoder->run())
return false;
cout << "Transcoder run: ";
printStatus(transcoder->error());
transcoder->close();
cout << "Transcoder close: ";
printStatus(transcoder->error());
}
else
{
printStatus(transcoder->error());
return false;
}
return true;
}
Complete C++ Code#
Here’s the complete working example that demonstrates H.264 encoding using AVBlocks. This code combines all the previous snippets into a functional program that can be compiled and run. The main function handles command-line argument parsing, initializes AVBlocks, performs the encoding operation, and properly shuts down the library before exiting.
#include <unistd.h>
#include <iostream>
#include <string>
#include <filesystem>
#include <primo/platform/reference++.h>
#include <primo/platform/error_facility.h>
#include <primo/platform/ustring.h>
#include <primo/avblocks/avb.h>
#include "options.h"
#include "util.h"
using namespace std;
using namespace primo::avblocks;
using namespace primo::codecs;
namespace fs = std::filesystem;
namespace av = primo::avblocks;
namespace pc = primo::codecs;
void printStatus(const primo::error::ErrorInfo* e)
{
if (primo::error::ErrorFacility::Success == e->facility())
{
cout << "Success";
}
else
{
if (e->message())
{
cout << primo::ustring(e->message()) << " ";
}
cout << "(facility:" << e->facility() << " error:" << e->code() << ")" << endl;
}
cout << endl;
}
primo::ref<MediaSocket> createInputSocket(Options& opt)
{
auto socket = primo::make_ref(Library::createMediaSocket());
socket->setStreamType(StreamType::UncompressedVideo);
socket->setFile(primo::ustring(opt.yuv_file));
auto pin = primo::make_ref(Library::createMediaPin());
socket->pins()->add(pin.get());
auto vsi = primo::make_ref(Library::createVideoStreamInfo());
pin->setStreamInfo(vsi.get());
vsi->setStreamType(StreamType::UncompressedVideo);
vsi->setFrameWidth(opt.frame_size.width_);
vsi->setFrameHeight(opt.frame_size.height_);
vsi->setColorFormat(opt.yuv_color.Id);
vsi->setFrameRate(opt.fps);
vsi->setScanType(ScanType::Progressive);
return socket;
}
primo::ref<MediaSocket> createOutputSocket(Options& opt)
{
auto socket = primo::make_ref(Library::createMediaSocket());
socket->setFile(primo::ustring(opt.h264_file));
socket->setStreamType(StreamType::H264);
auto pin = primo::make_ref(Library::createMediaPin());
socket->pins()->add(pin.get());
auto vsi = primo::make_ref(Library::createVideoStreamInfo());
pin->setStreamInfo(vsi.get());
vsi->setStreamType(StreamType::H264);
vsi->setStreamSubType(StreamSubType::AVC_Annex_B);
return socket;
}
bool encode(Options& opt)
{
// create input socket
auto inSocket = createInputSocket(opt);
// create output socket
auto outSocket = createOutputSocket(opt);
// create transcoder
auto transcoder = primo::make_ref(Library::createTranscoder());
transcoder->setAllowDemoMode(true);
transcoder->inputs()->add(inSocket.get());
transcoder->outputs()->add(outSocket.get());
// transcoder will fail if output exists (by design)
deleteFile(primo::ustring(opt.h264_file));
cout << "Transcoder open: ";
if(transcoder->open())
{
printStatus(transcoder->error());
if(!transcoder->run())
return false;
cout << "Transcoder run: ";
printStatus(transcoder->error());
transcoder->close();
cout << "Transcoder close: ";
printStatus(transcoder->error());
}
else
{
printStatus(transcoder->error());
return false;
}
return true;
}
int main(int argc, char* argv[])
{
Options opt;
switch(prepareOptions(opt, argc, argv))
{
case Command: return 0;
case Error: return 1;
case Parsed: break;
}
Library::initialize();
bool encodeResult = encode(opt);
Library::shutdown();
return encodeResult ? 0 : 1;
}
How to Run#
See the build instructions for macOS and the enc_avc_file example for details.
Command Line#
./enc_avc_file --frame <width>x<height> --rate <fps> --color <COLOR> --input <file.yuv> --output <file.h264> [--colors] [--help]
Examples#
List options:
./bin/x64/enc_avc_file --help
enc_avc_file --frame <width>x<height> --rate <fps> --color <COLOR> --input <file.yuv> --output <file.h264> [--colors]
-h, --help
-i, --input input YUV file
-o, --output output H264 file
-r, --rate input frame rate
-f, --frame input frame sizes <width>x<height>
-c, --color input color format. Use --colors to list all supported color
formats
--colors list COLOR constants
The following example encodes input file ./assets/vid/foreman_qcif.yuv into output file foreman_qcif.h264:
mkdir -p ./output/enc_avc_file
./bin/x64/enc_avc_file \
--input ./assets/vid/foreman_qcif.yuv \
--output ./output/enc_avc_file/foreman_qcif.h264 \
--frame 176x144 \
--rate 30 \
--color yuv420