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• Encode 256 Palletized bitmaps to h264 using libav

  12 février 2014, par user3239282

  Am converting 32 bpp bitmap to 8bpp with 256 color pallete, this image i want to encode using h264 and send it over socket. And on the other end decode the frame and display it on my UI.

  From Encoder, side :

  1. Capture 32 bpp image.
  2. Quantize the image to 8bpp with 256 color pallete.
  3. Sws_scale the image from PIX_FMT_GRAY8 to YUV420P.
  4. Encode it with h264 and send it over socket.

  From Decoder, side.

  1. Receive image.
  2. Decode image.
  3. Sws_scale from YUV420P to PIX_FMT_GRAY8
  4. And display it on UI along with palette information(Sent from Encoder over socket).

  When the above steps are followed, i get a totally distorted image. And when i dont use the color palette i get a black and white image.

  Am not not clear how to encode the 8bpp 256 palette bitmaps using h264 and decode them accordingly. Please help me regarding this.

  Am working with C++ on windows platform.

  Thanks in advance,
  Paul.

• HLS Playback Issues on Android with FFMPEG

  25 mai 2014, par Florian

  I am using the FFMPEG built of AppUnite with the latest patch for stagefright support in order to playback http live streams : https://review.appunite.com/#/c/1779/

  As the stream does not start at 0, I added the following code to avoid a black screen :

  struct Player {
  
     + int64_t video_start_time;
  
  }
  
  
  
  void player_get_video_duration(struct Player *player) {
  
  + player->video_start_time = 0;
  
  
  
  + for (i = 0; i < player->capture_streams_no; ++i) {
  
  +    AVStream *stream = player->input_streams[i];
  
  +       if (stream->start_time > 0) {
  
  +          player->video_start_time = av_rescale_q(
  
  +             stream->start_time, stream->time_base, AV_TIME_BASE_Q);
  
  +
  
  +          LOGI(3, "player_set_data_source stream[%d] start_time: %ld",
  
  +             i, player->video_start_time);
  
  +
  
  +           break;
  
  +       }
  
  +   }
  
  }
  
  
  
  enum WaitFuncRet player_wait_for_frame(
  
     struct Player *player, double time, int stream_no) {
  
  - int64_t current_time = av_gettime();
  
  + int64_t current_time = av_gettime() + player->video_start_time; 
  
  }

  However, as soon as the sleep_time in player_wait_for_frame drops below 0, playback freezes and then hangs waiting for a frame that never arrives. The queues allocated by player_alloc_queues function seem being not big enough to hold the real-time stream pushed in between player_open_input and player_start_decoding_threads. Increasing the number of nodes in the queue does not resolve the issue however. The issue seems to be clearly in the player_wait_for_frame method but I am unable to find a solution.

  I spent quite a lot time trying to resolve this nasty issue, but without success so far. Any help really appreciated !!!

• ffmpeg padding while leaving audio track unchanged

  17 janvier 2016, par mmj

  My cheap 16:9 TV is not able to play correctly a 1280x544 video (I see the 2.35:1 aspect ratio image vertically stretched to 16:9 aspect ratio, incomprehensibly the TV aspect ratio adjustment is disabled if source is USB), so I used ffmpeg (on Windows 10) to add two 88 pixels high horizontal black bars in order to get to a 1280x720 video with a 16:9 aspect ratio, using the following command :

  ffmpeg -i my_input_video.mkv -filter:v "pad=1280:720:0:88" my_output_video.mkv

  My TV play the new video correctly, but it says that the audio is not supported, whereas in the original video it was.

  How can I pad the original video leaving the audio track unchanged ?