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• omxplayer : audio out of sync

  31 janvier 2014, par Jan Pulpan

  We build simple web controlled video player based on Raspberry Pi and omxplayer. The problem we have is any file which is transcoded with ffmpeg has an audio out of sync. The video file produced at iPad and uploaded directly to Pi plays fine. The same file transcoded with simple ffmpeg command like this doesn't and audio is about 1s delayed :

  ffmpeg -i input.mp4 output.mp4

  The audio out of sync problem shows at Raspberry/omxplayer only. If I play the same file at computer it's perfectly fine. The input file is 720p h264 aac one.

  Anyone has solved something like this before ?

  Thanks !

• ffmpeg trimming video with -ss and -t working only with audio

  16 février 2014, par user3197974

  I am trying to extract 5 seconds out of a TS stream using the command below :

  ffmpeg -ss 780 -t 5 -i "D:\TS\stream_457.ts" -map 0:17 -map 0:7 -qscale 6 -y -async 1 "D:\1_O.ts"

  The trimming seems to work on the audio track, the output file plays only 5 seconds of audio but the video starts at second 780 and continues until the end of the stream. So i end up with 5 seconds of audio and 37 seconds of video.

  How can i trim both audio and video ?

  Thanks

• Decode audio using libavcodec and play using libAO ?

  21 mars 2012, par Ashika Umanga Umagiliya

  I use following code snippet to decode audio files (tested with MP3,WAV,WMV).

  But when it plays the audio , it just gives static sounds and crashes time to time.
  Any hints on what i am doing wrong here ?

  #include 
  
  #include 
  
  #include 
  
  #include 
  
  
  
  
  
  extern "C" {
  
  #include "libavutil/mathematics.h"
  
  #include "libavformat/avformat.h"
  
  #include "libswscale/swscale.h"
  
  #include <ao></ao>ao.h>
  
  
  
  }
  
  
  
  void die(const char *msg)
  
  {
  
      fprintf(stderr,"%s\n",msg);
  
      exit(1);
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
  
  
      const char* input_filename=argv[1];
  
  
  
      //avcodec_register_all();
  
      av_register_all();
  
      //av_ini
  
  
  
      AVFormatContext* container=avformat_alloc_context();
  
      if(avformat_open_input(&amp;container,input_filename,NULL,NULL)&lt;0){
  
          die("Could not open file");
  
      }
  
  
  
      if(av_find_stream_info(container)&lt;0){
  
          die("Could not find file info");
  
      }
  
      av_dump_format(container,0,input_filename,false);
  
  
  
      int stream_id=-1;
  
      int i;
  
      for(i=0;inb_streams;i++){
  
          if(container->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO){
  
              stream_id=i;
  
              break;
  
          }
  
      }
  
      if(stream_id==-1){
  
          die("Could not find Audio Stream");
  
      }
  
  
  
      AVDictionary *metadata=container->metadata;
  
  
  
      AVCodecContext *ctx=container->streams[stream_id]->codec;
  
      AVCodec *codec=avcodec_find_decoder(ctx->codec_id);
  
  
  
      if(codec==NULL){
  
          die("cannot find codec!");
  
      }
  
  
  
      if(avcodec_open(ctx,codec)&lt;0){
  
          die("Codec cannot be found");
  
      }
  
  
  
      //ctx=avcodec_alloc_context3(codec);
  
  
  
      //initialize AO lib
  
      ao_initialize();
  
  
  
      int driver=ao_default_driver_id();
  
  
  
      ao_sample_format sformat;
  
      sformat.bits=16;
  
      sformat.channels=2;
  
      sformat.rate=44100;
  
      sformat.byte_format=AO_FMT_NATIVE;
  
      sformat.matrix=0;
  
  
  
      ao_device *adevice=ao_open_live(driver,&amp;sformat,NULL);
  
      //end of init AO LIB
  
  
  
      AVPacket packet;
  
      av_init_packet(&amp;packet);
  
  
  
      AVFrame *frame=avcodec_alloc_frame();
  
  
  
      int buffer_size=AVCODEC_MAX_AUDIO_FRAME_SIZE;
  
      uint8_t buffer[buffer_size];
  
      packet.data=buffer;
  
      packet.size =buffer_size;
  
  
  
  
  
  
  
      int len;
  
      int frameFinished=0;
  
      while(av_read_frame(container,&amp;packet)>=0)
  
      {
  
  
  
          if(packet.stream_index==stream_id){
  
              //printf("Audio Frame read  \n");
  
              int len=avcodec_decode_audio4(ctx,frame,&amp;frameFinished,&amp;packet);
  
              //frame->
  
              if(frameFinished){
  
                  //printf("Finished reading Frame %d %d\n",packet.size,len);
  
                  ao_play(adevice, (char*)frame->data, len);
  
              }
  
  
  
          }
  
  
  
  
  
      }
  
  
  
      av_close_input_file(container);
  
      ao_shutdown();
  
      return 0;
  
  }