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Sur d’autres sites (9079)
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Decoding an MKA audio file into raw data (MKA Audio to raw audio data)
9 octobre 2020, par bbddMy task is to open an existing audio file with the
mkaextension (Matroska container) and extract the raw audio data. This example shows only an example of extracting raw data from anmp2file. I do not know how to do this with themkacontainer. I would like to have something like this :

UPD


I found an option to save audio data in the format in which it was recorded in the audio file. An example is shown below.


PS. This is only a test version and most likely there are memory leaks and other problems.



#include <qfile>
#include <qdebug>
#include "audiodecoder.h"

int main(int argc, char* argv[])
{
 AudioDecoder decoder("/home/test/test.mka");
 bool started = decoder.start();
 if (!started) {
 return EXIT_FAILURE;
 }

 QFile file("/home/test/rawData.bin");
 file.open(QIODevice::WriteOnly);

 while (true) {
 auto data = decoder.getData(255);
 if (data.isEmpty()) {
 break;
 }
 file.write(data.data(), data.size());
 }
 file.close();
 return EXIT_SUCCESS;
}

</qdebug></qfile>

audiodecoder.h


class AudioDecoder {
public:
 AudioDecoder(const QString& fileName);
 AudioDecoder& operator=(const AudioDecoder& rhs) = delete;
 AudioDecoder& operator=(AudioDecoder&& rhs) = delete;
 AudioDecoder(const AudioDecoder& rhs) = delete;
 AudioDecoder(AudioDecoder&& rhs) = delete;
 virtual ~AudioDecoder(void);

 virtual bool start(void) noexcept;
 virtual QByteArray getData(const quint16& size) noexcept;
 virtual bool stop(void) noexcept;

protected:
 bool m_initialized;
 QString m_fileName;

 AVFrame* p_frame = nullptr;
 AVPacket* p_packet = nullptr;
 AVCodecContext* p_cdcCtx = nullptr;
 AVFormatContext* p_frmCtx = nullptr;
};


audiodecoder.cpp



static void logging(const char* message)
{
 qDebug() << message;
}

AudioDecoder::AudioDecoder(const QString& fileName)
 : m_initialized(false)
 , m_fileName(fileName)
 , p_cdcCtx(nullptr)
 , p_frmCtx(nullptr)
{
 av_register_all();
}

QByteArray AudioDecoder::getData(const quint16& dataSize) noexcept
{
 QByteArray data;
 qint32 response = 0;
 if (av_read_frame(p_frmCtx, p_packet) >= 0) {
 //logging(QString("AVPacket->pts %1").arg(p_packet->pts).toStdString().c_str());
 //response = decode_packet(p_packet, p_cdcCtx, p_frame);
 response = avcodec_send_packet(p_cdcCtx, p_packet);
 if (response < 0) {
 logging("Error while sending a packet to the decoder");
 return {};
 }
 while (response >= 0) {
 response = avcodec_receive_frame(p_cdcCtx, p_frame);
 if (response == AVERROR(EAGAIN) || response == AVERROR_EOF) {
 break;
 }
 else if (response < 0) {
 logging("Error while receiving a frame from the decoder");
 return {};
 }
 if (response >= 0) {
 logging(QString("Frame %1 (type=%2, size=%3 bytes) pts %4 key_frame %5 [DTS %6], duration[%7]")
 .arg(p_cdcCtx->frame_number)
 .arg(av_get_picture_type_char(p_frame->pict_type))
 .arg(p_frame->pkt_size)
 .arg(p_frame->pts)
 .arg(p_frame->key_frame)
 .arg(p_frame->coded_picture_number)
 .arg(p_frame->pkt_duration)
 .toStdString()
 .c_str());

 for (int i = 0; i < p_frame->linesize[0]; ++i) {
 data.push_back(p_frame->data[0][i]);
 }
 }
 }
 av_packet_unref(p_packet);
 return data;
 }
 return {};
}

bool AudioDecoder::start(void) noexcept
{
 if (m_initialized) {
 return true;
 }

 int error;
 // Open the input file to read from it.
 if ((error = avformat_open_input(&p_frmCtx,
 m_fileName.toStdString().c_str(), nullptr, nullptr))
 < 0) {
 qDebug() << "Could not open input file: " << m_fileName;
 p_frmCtx = nullptr;
 return false;
 }
 // Get information on the input file (number of streams etc.).
 if ((error = avformat_find_stream_info(p_frmCtx, nullptr)) < 0) {
 avformat_close_input(&p_frmCtx);
 qDebug() << __LINE__;
 return false;
 }
 // Make sure that there is only one stream in the input file.
 if ((p_frmCtx)->nb_streams != 1) {
 avformat_close_input(&p_frmCtx);
 qDebug() << __LINE__;
 return false;
 }

 if (p_frmCtx->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_AUDIO) {
 avformat_close_input(&p_frmCtx);
 qDebug() << __LINE__;
 return false;
 }

 // Find a decoder for the audio stream.
 AVCodec* input_codec = nullptr;
 if (!(input_codec = avcodec_find_decoder((p_frmCtx)->streams[0]->codecpar->codec_id))) {
 avformat_close_input(&p_frmCtx);
 qDebug() << __LINE__;
 return false;
 }
 // Allocate a new decoding context.
 AVCodecContext* avctx = avcodec_alloc_context3(input_codec);
 if (!avctx) {
 avformat_close_input(&p_frmCtx);
 qDebug() << __LINE__;
 return false;
 }
 // Initialize the stream parameters with demuxer information.
 error = avcodec_parameters_to_context(avctx, (p_frmCtx)->streams[0]->codecpar);
 if (error < 0) {
 avformat_close_input(&p_frmCtx);
 avcodec_free_context(&avctx);
 qDebug() << __LINE__;
 return false;
 }
 /* Open the decoder for the audio stream to use it later. */
 if ((error = avcodec_open2(avctx, input_codec, NULL)) < 0) {
 avcodec_free_context(&avctx);
 avformat_close_input(&p_frmCtx);
 qDebug() << __LINE__;
 return false;
 }
 /* Save the decoder context for easier access later. */
 p_cdcCtx = avctx;
 av_dump_format(p_frmCtx, 0, m_fileName.toStdString().c_str(), 0);

 p_frame = av_frame_alloc();
 if (!p_frame) {
 logging("failed to allocated memory for AVFrame");
 return false;
 }
 p_packet = av_packet_alloc();
 if (!p_packet) {
 logging("failed to allocated memory for AVPacket");
 return false;
 }
 return m_initialized = true;
}

bool AudioDecoder::stop(void) noexcept
{
 if (p_cdcCtx != nullptr) {
 avcodec_free_context(&p_cdcCtx);
 }
 if (p_frmCtx != nullptr) {
 avformat_close_input(&p_frmCtx);
 }
 return true;
}

AudioDecoder::~AudioDecoder(void)
{
 stop();
}


But the problem in this example is that I didn't implement the ability to get exactly the requested size of audio data. In my case, it's just ignored.


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H264 - how to interpret encoded video data [closed]
30 décembre 2024, par Ragdoll CarI would like to know how to interpret encoded video data by H.264 codec e.g. FFmpeg's
AVPacket.data.

Are there any good resources about that to study ?


I've been looking for the Internet, but I didn't find any documentation about H.264 format.


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How to extract EPG data from a rec/ts file ?
5 janvier 2016, par wolfrevoI need to extract the data stream of a rec/ts file.
What I’ve tried until now is withavconvavconv -i filename.recI get this output
avconv version 0.8.17-6:0.8.17-1, Copyright (c) 2000-2014 the Libav developers
built on Mar 15 2015 17:00:31 with gcc 4.7.2
...
Input #0, mpegts, from 'filename.rec':
Duration: 01:54:55.94, start: 74083.801633, bitrate: 400 kb/s
...
Program 28479
Metadata:
...
Stream #0.0[0x475](ger): Audio: mp2, 48000 Hz, stereo, s16, 320 kb/s
Stream #0.1[0x81a]: Data: [5][0][0][0] / 0x0005
Stream #0.2[0x881]: Data: [11][0][0][0] / 0x000B
...AFIK the data stream contains the EPG information. Does it ?
The following command
avconv -i filename.rec -f ffmetadata metadata.txtoutputs this to metadata.txt
;FFMETADATA1and with
avconv -i filename.rec -map 0:1 -f ffmetadata metadata.txtI get the message
Data stream encoding not supported yet (only streamcopy)The file
filename.rechas following content which I would like to extract :
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