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• Encode images to video by using ffmpeg API？

  18 avril 2013, par Super Astro

  I want to encode some image files into one video file, and play each image for 1 second.

  So I wrote a simple function to encode only one image to a video

      void PhotoStory::test(char* imagefile,char* videoFile)
  
  {
  
      av_register_all();
  
      avcodec_register_all();
  
      AVCodecContext          *pOCtx= NULL;
  
      AVCodec                 *pOCodex = NULL;
  
      pOCodex = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);
  
      pOCtx= avcodec_alloc_context3(pOCodex);
  
  
  
      pOCtx->bit_rate = 400000;
  
      pOCtx->width = 640;
  
      pOCtx->height = 480;
  
      AVRational rational = {1,25};
  
      pOCtx->time_base= rational;
  
      pOCtx->gop_size = 10; /* emit one intra frame every ten frames */
  
      pOCtx->max_b_frames=1;
  
      pOCtx->pix_fmt = PIX_FMT_YUV420P;
  
  
  
  
  
      int ret = avcodec_open2(pOCtx,pOCodex,NULL);
  
      if(ret < 0)
  
      {
  
           return;
  
      }
  
  
  
      AVFormatContext         *pIFormatCtx = NULL;
  
       ret = avformat_open_input(&pIFormatCtx, imagefile, NULL, NULL);
  
      if(ret < 0)
  
      {
  
          //Cant't open jpg file
  
          return;
  
      }
  
      av_dump_format(pIFormatCtx, 0, imagefile, false);
  
  
  
      AVCodecContext          *pICodecCtx;  //output codec context
  
      pICodecCtx = pIFormatCtx->streams[0]->codec;
  
      /*pICodecCtx->width = 640;
  
      pICodecCtx->height = 480;
  
      pICodecCtx->pix_fmt = PIX_FMT_YUV420P;*/
  
  
  
  
  
      AVCodec *pICodec = avcodec_find_decoder(pICodecCtx->codec_id); //output codec
  
       // Open codec
  
      ret = avcodec_open2(pICodecCtx, pICodec,NULL);
  
      if(ret < 0)
  
      {
  
          //Can't find the decoder
  
          return;
  
      }
  
  
  
      AVFrame *pIFrame = avcodec_alloc_frame();
  
      if (!pIFrame)
  
      {
  
          //Can't alloc the input frame
  
          return ;
  
      }
  
  
  
  
  
      int bufSize = avpicture_get_size(PIX_FMT_YUVJ420P, pICodecCtx->width, pICodecCtx->height);
  
      uint8_t *buffer = (uint8_t *) av_malloc(bufSize * sizeof(uint8_t));
  
  
  
      avpicture_fill((AVPicture *) pIFrame, buffer, PIX_FMT_YUVJ420P, pICodecCtx->width, pICodecCtx->height);
  
  
  
      FILE *outputFile;
  
      if(fopen_s(&outputFile,videoFile,"wb") < 0)
  
      {
  
          //TODO open file error
  
      }
  
  
  
      int outbuf_size = 100000;
  
      outbuf = (uint8_t*)malloc(outbuf_size);
  
  
  
  
  
  
  
  
  
      AVPacket packet;
  
      int frameFinished;
  
      int framesNumber = 0;
  
      while (av_read_frame(pIFormatCtx, &packet) >= 0)
  
      {
  
          if(packet.stream_index != 0)
  
              continue;
  
  
  
          ret = avcodec_decode_video2(pICodecCtx, pIFrame, &frameFinished, &packet);
  
          if (ret > 0)
  
          {
  
              pIFrame->quality = 4;
  
  
  
              for(i=0;i<25;i++) {
  
                  fflush(stdout);
  
                  /* encode the image */
  
                  out_size = avcodec_encode_video(pOCtx, outbuf, outbuf_size, pIFrame);
  
                  fwrite(outbuf, 1, out_size, outputFile);
  
              }
  
          }
  
      }
  
  
  
      /* get the delayed frames */
  
      for(; out_size; i++) {
  
          fflush(stdout);
  
          out_size = avcodec_encode_video(pOCtx, outbuf, outbuf_size, NULL);
  
          fwrite(outbuf, 1, out_size, outputFile);
  
      }
  
  
  
      /* add sequence end code to have a real mpeg file */
  
      outbuf[0] = 0x00;
  
      outbuf[1] = 0x00;
  
      outbuf[2] = 0x01;
  
      outbuf[3] = 0xb7;
  
      fwrite(outbuf, 1, 4, outputFile);
  
      fclose(outputFile);
  
      free(outbuf);
  
  
  
      avcodec_close(pOCtx);
  
      av_free(pOCtx);
  
      av_free(pIFrame);
  
  }

  but, the result seems not correct.
  the output file is only 4 bits.

  Anybody can help me to figure out the problem and correct the function ?

  thanks !

• Encoded images into H264 video are skipped and/or missing ?

  25 juillet 2013, par Jona

  I'm trying to encode images into an H264 MP4 video. The issues I'm having is that some of the images are skipped or at the end of the video simply missing. I need the video to play every single image I encode since it is an animation.

  Any help setting the encoder properly would be greatly appreciated !

  Encoder settings :

  AVCodecContext *c;
  
  ...
  
  c->codec_id = AV_CODEC_ID_H264;
  
  c->bit_rate = mOutputWidth*mOutputHeight*4;//400000;
  
  /* Resolution must be a multiple of two. */
  
  c->width    = mOutputWidth;
  
  c->height   = mOutputHeight;
  
      /* timebase: This is the fundamental unit of time (in seconds) in terms
  
       * of which frame timestamps are represented. For fixed-fps content,
  
       * timebase should be 1/framerate and timestamp increments should be
  
       * identical to 1. */
  
  c->time_base.den = mFps;
  
  c->time_base.num = 1;
  
  c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
  
  c->pix_fmt       = AV_PIX_FMT_YUV420P;
  
  ...
  
  av_dict_set(&pOptions, "preset", "medium", 0);
  
  av_dict_set(&pOptions, "tune", "animation", 0);
  
  
  
  /* open the codec */
  
  ret = avcodec_open2(c, codec, &pOptions);
  
  if (ret < 0) {
  
      LOGE("Could not open video codec: %s", av_err2str(ret));
  
      return -1;
  
  }

  Update 07/24/13 :
  I was able to achieve a better video by setting the gop_size=FPS and writing the last video frame repeatedly FPS+1 times seemed to resolve all issues. To me it seems odd to do that but might be something standard in the video encoding world ? Any tips feedback about this ?

• Convert MPEG4 to MPEGTS on Android with FFmpeg

  3 juin 2013, par Ardoramor

  Ok, so obviously I know very little to none about ffmpeg API when I made the original post... it is quite overwhelming when one starts learning about digital media and conversion details. After reading quite a bit more and going through ffmpeg source, I was able to get a working output from mp4 to mpegts. The concept is similar to executing :

  ffmpeg -i in.mp4 -vcodec copy -acodec copy -vbsf h264_mp4toannexb out.ts

  But as I mentioned before, I need to implement it with ffmpeg API in C.

  So, although I am able to generate a playable .ts file, its video and audio streams are not synced. That is, playing them back on Android tablet plays the video very slowly while audio is playing at normal speed and then (once audio stream ends) video plays at normal speed to the end. Playing the same generated .ts file in VLC produces a very condensed audio (as though fast-forwarded) and plays video fine.

  There are still many aspects of media conversion that I am not familiar with. I am sure that some of them prevent me from successful conversion.

  Here is some information (via ffprobe) about the files :
   in.mp4 - file generated via Android recording - MPEG4 (H.264 + AAC)
   ffmpeg.ts - file generated via ffmpeg conversion - MPEG2TS (H.264 + AAC)
   out.ts - file generated via my code - MPEGTS (H.264 + AAC)

  in.mp4

  filename=in.mp4
  
  nb_streams=2
  
  format_name=mov,mp4,m4a,3gp,3g2,mj2
  
  format_long_name=QuickTime/MPEG-4/Motion JPEG 2000 format
  
  start_time=0:00:00.000000
  
  duration=0:00:09.961383
  
  size=4.730 Mibyte
  
  bit_rate=3.983 Mbit/s
  
  TAG:major_brand=isom
  
  TAG:minor_version=0
  
  TAG:compatible_brands=isom3gp4
  
  TAG:creation_time=2013-05-28 17:06:57

  ffmpeg.ts

  filename=ffmpeg.ts
  
  nb_streams=2
  
  format_name=mpegts
  
  format_long_name=MPEG-2 transport stream format
  
  start_time=0:00:01.400000
  
  duration=0:00:09.741267
  
  size=5.132 Mibyte
  
  bit_rate=4.419 Mbit/s

  out.ts

  filename=out.ts
  
  nb_streams=2
  
  format_name=mpegts
  
  format_long_name=MPEG-2 transport stream format
  
  start_time=0:00:00.000000
  
  duration=0:00:09.741267
  
  size=5.166 Mibyte
  
  bit_rate=4.449 Mbit/s

  Firstly, I was unable to affect my output file's start_time. Next, upon examining the -show_packets output of probe, I saw the following :

  ffmpeg.ts

  [PACKET]
  
  codec_type=video
  
  stream_index=0
  
  pts=N/A
  
  pts_time=N/A
  
  dts=N/A
  
  dts_time=N/A
  
  duration=0
  
  duration_time=0:00:00.000000
  
  size=20.506 Kibyte
  
  pos=564
  
  flags=K
  
  [/PACKET]
  
  [PACKET]
  
  codec_type=video
  
  stream_index=0
  
  pts=N/A
  
  pts_time=N/A
  
  dts=N/A
  
  dts_time=N/A
  
  duration=0
  
  duration_time=0:00:00.000000
  
  size=11.727 Kibyte
  
  pos=22936
  
  flags=_
  
  [/PACKET]
  
  ...
  
  [PACKET]
  
  codec_type=audio
  
  stream_index=1
  
  pts=126000
  
  pts_time=0:00:01.400000
  
  dts=126000
  
  dts_time=0:00:01.400000
  
  duration=2089
  
  duration_time=0:00:00.023211
  
  size=285.000 byte
  
  pos=109416
  
  flags=K
  
  [/PACKET]
  
  [PACKET]
  
  codec_type=audio
  
  stream_index=1
  
  pts=128089
  
  pts_time=0:00:01.423211
  
  dts=128089
  
  dts_time=0:00:01.423211
  
  duration=2089
  
  duration_time=0:00:00.023211
  
  size=374.000 byte
  
  pos=-1
  
  flags=K
  
  [/PACKET]
  
  ...
  
  [PACKET]
  
  codec_type=video
  
  stream_index=0
  
  pts=N/A
  
  pts_time=N/A
  
  dts=N/A
  
  dts_time=N/A
  
  duration=0
  
  duration_time=0:00:00.000000
  
  size=20.000 Kibyte
  
  pos=87232
  
  flags=_
  
  [/PACKET]
  
  [PACKET]
  
  codec_type=video
  
  stream_index=0
  
  pts=N/A
  
  pts_time=N/A
  
  dts=N/A
  
  dts_time=N/A
  
  duration=0
  
  duration_time=0:00:00.000000
  
  size=16.852 Kibyte
  
  pos=112800
  
  flags=_
  
  [/PACKET]

  out.ts

  [PACKET]
  
  codec_type=audio
  
  stream_index=1
  
  pts=0
  
  pts_time=0:00:00.000000
  
  dts=0
  
  dts_time=0:00:00.000000
  
  duration=2089
  
  duration_time=0:00:00.023211
  
  size=285.000 byte
  
  pos=22936
  
  flags=K
  
  [/PACKET]
  
  [PACKET]
  
  codec_type=audio
  
  stream_index=1
  
  pts=1024
  
  pts_time=0:00:00.011378
  
  dts=1024
  
  dts_time=0:00:00.011378
  
  duration=2089
  
  duration_time=0:00:00.023211
  
  size=374.000 byte
  
  pos=23312
  
  flags=K
  
  [/PACKET]
  
  ...
  
  
  
  [PACKET]
  
  codec_type=video
  
  stream_index=0
  
  pts=N/A
  
  pts_time=N/A
  
  dts=N/A
  
  dts_time=N/A
  
  duration=0
  
  duration_time=0:00:00.000000
  
  size=11.727 Kibyte
  
  pos=25004
  
  flags=_
  
  [/PACKET]
  
  [PACKET]
  
  codec_type=audio
  
  stream_index=1
  
  pts=7168
  
  pts_time=0:00:00.079644
  
  dts=7168
  
  dts_time=0:00:00.079644
  
  duration=2089
  
  duration_time=0:00:00.023211
  
  size=299.000 byte
  
  pos=55460
  
  flags=K
  
  [/PACKET]

  As you can see, ffmpeg.ts starts out with video packets that do not have pts/dts. The audio packets that follow contain pts/dts. This repeats until the end. All video packets do not have pts/dts according to ffprobe output.

  However, out.ts starts with audio packets and alternate with video packets. Here, video packets also do not have pts/dts. The difference is that here there is one video packet between a series of audio packets. What happened to the rest of the video packets (ffmpeg.ts has 5 audio followed by 5 video).

  Obviously, I'm still learning and don't know way too much yet... Does anything jump out as obvious a problem to anyone ? I will greatly appreciate any info / suggestions but will continue to grind at it !!