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• Why the source order matters on working with multiple media sources in a single AVFormatContext ?

  24 avril 2024, par Mehmet YILMAZ

  avformat_open_input() deletes the AVFormatContext* and returns -6 when the source order changes.

  


  I am trying to open multiple media sources dynamically with different(mixed) formats and codecs in a single context (AVFormatContext).

  


  My media sources are a BlackMagic DeckLink Duo SDI input as first source and an mp4 file or rtsp stream as second.

  


  When I order to open (avformat_open_input()) the source 2 (RTSP or MP4 file) at first and then open the BlackMagic DeckLink Duo, proceed as expected.

  


  But when I change the order, and first open the DeckLink and then try to open RTSP stream or MP4 file, as I inspected in the step debugger ; AVFormatContext* deleting in the av_open_input() function and it returns -6 as result.

  


  Please find the simple error reproduction code snappet below ;

  


  AVFormatContext* context{avformat_alloc_context()};
const char* url_source1{"DeckLink Duo (1)"};
const AVInputFormat* format_source1{av_find_input_format("decklink")};

const char* url_source2{"http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4"};

// Open the first media input
int result = avformat_open_input(&context, url_source1, format_source1, NULL);

if(result < 0) {
  exit(1);
}

// Open the second media input
// This function in current order deletes the context and returns -6
result = avformat_open_input(&context, url_source2, NULL, NULL);
if(result < 0) {
  exit(1);
}

// Since the context has been deleted in previous step, segmentation fault accours here!
result = avformat_find_stream_info(context, NULL);
if(result < 0) {
  exit(1);
}

std::cout << "Total number of streams: " << context->nb_streams << std::endl;



  


  But When I change the order and call the avformat_open_input() first for the mp4 file and then the DeckLink device as following it proceed as expected, no error.

  


  AVFormatContext* context{avformat_alloc_context()};
const char* url_source1{"DeckLink Duo (1)"};
const AVInputFormat* format_source1{av_find_input_format("decklink")};

const char* url_source2{"http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4"};


// Open the second media input
int result = avformat_open_input(&context, url_source2, NULL, NULL);
if(result < 0) {
  exit(1);
}


// Open the first media input
result = avformat_open_input(&context, url_source1, format_source1, NULL);

if(result < 0) {
  exit(1);
}


result = avformat_find_stream_info(context, NULL);
if(result < 0) {
  exit(1);
}

std::cout << "Total number of streams: " << context->nb_streams << std::endl;



  


• build : arm : cosmetics : Place all OBJS declarations in alphabetical order

  29 mai 2013, par Diego Biurrun

  build : arm : cosmetics : Place all OBJS declarations in alphabetical order
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/arm/Makefile

• FFmpeg command to transcode video in order to bypass YouTube Content ID

  18 août 2015, par 阿尔曼

  This is the code I use to crop and add subtitles to the video :

  ffmpeg -y -i VTS_01_1.VOB -filter_complex "[0:v] crop=720:432:0:72 [crop]; [crop] ass=VTS_01.ass" -c:v libx264 -c:a aac -strict -2 output.mp4

  and this is the result I published on YouTube :

  https://www.youtube.com/watch?v=8vwUFO9uF-U

  My problem : Some of the videos received Content ID claim and were blocked in 244 countries, for example :

  https://www.youtube.com/watch?v=IVt24GLmfVY

  My question : Is it possible to transcode video a little bit with FFmpeg in order to bypass YouTube Content ID and how to do it ?