[Libav-user] FFMpeg - x264

[Rouhi Amirhossein]

Hi
I dont know the answer but i have a question. I would be pleased if you let
me know how can i use FFMPEG functions in my program? I do programming in C
and i call ffmpeg command line by "system()" function in C. But for using
some specific functions, i actually dont know how to do it in windows os.
would you let me know?
Thanks
Amir

On 15 September 2011 04:31, Denis <info at denisgottardello.it> wrote:

> **
>
> In data mercoledì 14 settembre 2011 17:44:34, Roger Pack ha scritto:
>
> > > Vlc does not work.
>
> > > Wich is the error? I can not to find it. I can not understand wich is
> the
>
> > > right way for store a frame in a h264 file.
>
> >
>
> > Maybe you're setting the pts timestamps wrong?
>
>  I have made a small step forward. Now I can produce a h264 file that I
> can see with mplayer and vlc but I have some trouble.
>
> Mplayer plays the video at 50 fps instead of 25. Vlc plays the video at the
> right fps.
>
> Another program says that the video has a wrong timestamp (pts dts). This
> is what the program says:
>
> PachetCount: 1 , 6144 bytes, pBufferSize: 32768
>
> PachetCount: 2 , 26624 bytes, pBufferSize: 26624
>
> [mpegts @ 0xb2502da0] Invalid timestamps stream=0, pts=0, dts=8589927392,
> size=1163
>
> [mpegts @ 0xb2502da0] Invalid timestamps stream=0, pts=14400, dts=
> 8589930992, size=19
>
> [mpegts @ 0xb2502da0] max_analyze_duration 5000000 reached at 5000000
>
> [mpegts @ 0xb2502da0] Estimating duration from bitrate, this may be
> inaccurate
>
> dump_format begin
>
> Input #0, mpegts, from 'foo.mpg':
>
> Duration: N/A, start: 0.000000, bitrate: N/A
>
> Program 1
>
> Metadata:
>
> service_name : Service01
>
> service_provider: FFmpeg
>
> Stream #0.0[0x100]: Video: h264 (High), yuv420p, 320x240, 25 fps, 25 tbr,
> 90k tbn, 50 tbc
>
> dump_format end
>
> 0
>
> "fps: 25"
>
> And this is the function:
>
> void QThCamera::run() {
>
> qDebug() << "QThCamera::run() start";
>
> QString MPGFileName= "a.mpg", MJPEGFileName= "a.mjpg";
>
>  CvCapture *Capture= NULL;
>
> Capture= cvCreateCameraCapture(Index, Width, Height);
>
> if (!Capture) qDebug() << "Cannot open or initialize webcam!";
>
> else {
>
> if (ExternalFrame) cvNamedWindow("Frame", CV_WINDOW_AUTOSIZE);
>
> IplImage *frame= 0;
>
> CvFont font;
>
> cvInitFont(&font, CV_FONT_HERSHEY_SIMPLEX, 0.5f, 0.5f);
>
>  AVOutputFormat *pOutputFormat= av_guess_format("mpegts", NULL, NULL);
>
> if (!pOutputFormat) {
>
> qDebug() << "Could not set output format, using MPEG.";
>
> pOutputFormat= av_guess_format("mpeg", NULL, NULL);
>
> }
>
> if (!pOutputFormat) qDebug() << "Could not set output format.";
>
> else {
>
> AVFormatContext *pFormatCtx;
>
> if (avformat_alloc_output_context2(&pFormatCtx, pOutputFormat, NULL, NULL
> )< 0) qDebug() << "avformat_alloc_output_context2 Error!";
>
> else {
>
> AVStream *pVideoStream= av_new_stream(pFormatCtx, 0);
>
> if (!pVideoStream) qDebug() << "av_new_stream Error!";
>
> else {
>
> AVCodecContext *pCodecCtx= pVideoStream->codec;
>
> pCodecCtx->codec_id= CODEC_ID_H264;
>
> pCodecCtx->codec_type= AVMEDIA_TYPE_VIDEO;
>
> pCodecCtx->bit_rate= 40000;
>
> pCodecCtx->width= Width;
>
> pCodecCtx->height= Height;
>
> pCodecCtx->time_base.den= 25;
>
> pCodecCtx->time_base.num= 1;
>
> pCodecCtx->gop_size= 10;
>
> pCodecCtx->pix_fmt= PIX_FMT_YUV420P;
>
> if (pFormatCtx->oformat->flags & AVFMT_GLOBALHEADER) pCodecCtx->flags |=
> CODEC_FLAG_GLOBAL_HEADER;
>
> av_dump_format(pFormatCtx, 0, MPGFileName.toStdString().c_str(), 1);
>
> AVCodec *pCodec= avcodec_find_encoder(pCodecCtx->codec_id);
>
> if (!pCodec) qDebug() << "avcodec_find_encoder Error!";
>
> else {
>
> if (avcodec_open(pCodecCtx, pCodec)< 0) qDebug() << "avcodec_open Error!";
>
> else {
>
> if (avio_open(&pFormatCtx->pb, MPGFileName.toStdString().c_str(),
> AVIO_FLAG_WRITE)< 0) qDebug() << "url_fopen Error!";
>
> else {
>
> if (avformat_write_header(pFormatCtx, NULL)!= 0) qDebug() <<
> "av_write_header Error!";
>
> int BYTEPIC= Width * Height * 3;
>
> uint8_t *pOutBuffer= (uint8_t*)malloc(BYTEPIC); {
>
> QFile QFFileOut;
>
> QFFileOut.setFileName(MJPEGFileName);
>
> QFFileOut.open(QIODevice::WriteOnly);
>
> int Frames= 0;
>
> QDateTime QDTStart= QDateTime::currentDateTime();
>
> while (DoStart) {
>
> if (!cvSetChannel(Capture, Channel)) qDebug() << "Unable to set channel.";
>
> frame= cvQueryFrame(Capture);
>
> if (frame) {
>
> if (MainForm->ui->QCBAutoBrightness->isChecked()) {
>
> int Brightness= BrightnessOfAPixel(frame);
>
> Brightness= ((Brightness * 200 / 256) - 100) * -1;
>
> IplImage *frame2= ContrastBrightness(frame, 0, Brightness); {
>
> cvCopyImage(frame2, frame);
>
> }{
>
> cvReleaseImage(&frame2);
>
> }
>
> } else {
>
> IplImage *frame2= ContrastBrightness(frame, MainForm->ui->QHSContrast->
> value(), MainForm->ui->QHSBrightness->value()); {
>
> cvCopyImage(frame2, frame);
>
> }{
>
> cvReleaseImage(&frame2);
>
> }
>
> }
>
> if (MainForm->ui->QCBShowDateTime->isChecked()) cvPutText(frame, QDateTime
> ::currentDateTime().toString("dd-MM-yyyy hh:mm:ss").toAscii(), cvPoint(10,
> 20), &font, cvScalar(255, 255, 255));
>
> if (MainForm->ui->QRBRotate90->isChecked()) {
>
> IplImage *frame2= Rotate(frame, 90); {
>
> cvCopyImage(frame2, frame);
>
> }{
>
> cvReleaseImage(&frame2);
>
> }
>
> } else if (MainForm->ui->QRBRotate180->isChecked()) {
>
> IplImage *frame2= Rotate(frame, 180); {
>
> cvCopyImage(frame2, frame);
>
> }{
>
> cvReleaseImage(&frame2);
>
> }
>
> } else if (MainForm->ui->QRBRotate270->isChecked()) {
>
> IplImage *frame2= Rotate(frame, 270); {
>
> cvCopyImage(frame2, frame);
>
> }{
>
> cvReleaseImage(&frame2);
>
> }
>
> }
>
> if (ExternalFrame) cvShowImage("Frame", frame);
>
> QImage Image(frame->width, frame->height, QImage::Format_RGB888);
>
> const unsigned char *data= NULL;
>
> data= (unsigned char*)(frame->imageData);
>
> Image= QImage(data, frame->width, frame->height, frame->widthStep, QImage
> ::Format_RGB888);
>
> if (DoStart) emit SendNewImage(Image);
>
>  QByteArray ByteArray;
>
> QBuffer Buffer(&ByteArray);
>
> Image.save(&Buffer, "JPG");
>
> QFFileOut.write(ByteArray);
>
> QFFileOut.write(QDateTime::currentDateTime().toString("yyyyMMddhhmmsszzz"
> ).toAscii());
>
>  AVFrame *pAVFrame= avcodec_alloc_frame();
>
> uint8_t *pBuffer= (uint8_t*)malloc(avpicture_get_size(PIX_FMT_YUV420P,
> Width, Height)); {
>
> avpicture_fill((AVPicture*)pAVFrame, pBuffer, PIX_FMT_YUV420P, Width,
> Height);
>
> IplImageToAVFrame(frame, pAVFrame, Width, Height, PIX_FMT_YUV420P);
>
> pAVFrame->pts= Frames;
>
> int OutSize= avcodec_encode_video(pCodecCtx, pOutBuffer, BYTEPIC,
> pAVFrame);
>
> if (OutSize> 0) {
>
> AVPacket Packet;
>
> av_init_packet(&Packet);
>
> if (pCodecCtx->coded_frame->pts != AV_NOPTS_VALUE) {
>
> Packet.pts= av_rescale_q(pCodecCtx->coded_frame->pts, pCodecCtx->time_base
> , pVideoStream->time_base);
>
> }
>
> //if (pCodecCtx->coded_frame->key_frame) Packet.flags |= AV_PKT_FLAG_KEY;
>
> Packet.stream_index= pVideoStream->index;
>
> Packet.data= pOutBuffer;
>
> Packet.size= OutSize;
>
> if (av_interleaved_write_frame(pFormatCtx, &Packet)!= 0) qDebug() <<
> "av_interleaved_write_frame Error!";
>
> }
>
> Frames++;
>
> if (Frames> pCodecCtx->time_base.den / pCodecCtx->time_base.num * 10)
> break;
>
> }{
>
> av_free(pAVFrame);
>
> free(pBuffer);
>
> }
>
>  } else qDebug() << "QThCamera::run() frame= false";
>
> }
>
> QFFileOut.close();
>
> qDebug() << Frames / QDTStart.secsTo(QDateTime::currentDateTime());
>
> }{
>
> free(pOutBuffer);
>
> }
>
> if (av_write_trailer(pFormatCtx)!= 0) qDebug() << "av_write_header Error!"
> ;
>
> avio_close(pFormatCtx->pb);
>
> }
>
> avcodec_close(pVideoStream->codec);
>
> }
>
> }
>
> for (int count= 0; (unsigned)count< pFormatCtx->nb_streams; count++) {
>
> av_freep(&pFormatCtx->streams[count]->codec);
>
> av_freep(&pFormatCtx->streams[count]);
>
> }
>
> }
>
> av_free(pFormatCtx);
>
> }
>
> }
>
> cvReleaseCapture(&Capture);
>
> if (ExternalFrame) cvDestroyWindow("Frame");
>
> }
>
> qDebug() << "QThCamera::run() stop";
>
> }
>
>   Now, if I have understand, all works in this mode:
>
> 1) In order to encode something with FFMpeg you must define a
> AVFormatContext object, that is a container.
>
> 2) Use "av_guess_format("mpegts", NULL, NULL);" for explain wich is the
> container type. In this case "mpegts" means mpeg4.
>
> 3) In the container you must define a stream that can be CODEC_ID_H264
>
> 4) With "av_interleaved_write_frame(pFormatCtx, &Packet)" you can insert a
> packet that contains a frame in the stream.
>
> Is that right?
>
> That I not have understand is: The pts and dts values must be express at
> container level? Stream level? Frame level? Packet level?
>
> Wich is the right way to calculate pts and dts value?
>
> The only thing that I do is this "pAVFrame->pts= Frames;" in order to not
> obtain this error: "non-strictly-monotonic PTS"
>
>  --
>
> www.denisgottardello.it
>
> Skype: mrdebug
>
> Videosurveillance and home automation!
>
> http://www.denisgottardello.it/DomusBoss/DomusBossIndice.php
>
> _______________________________________________
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>
>
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