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• Transcode video with ffmpeg can't play by Win10 system player ?

  16 juin 2017, par wzjing

   I’m doing a video transcoder demo with ffmpeg lib and libx264 lib. I already can transcode video successully, but the output video can only play by some powerful player like VLC. I need it can be played by the Win10 system player and the Android system player. I hava found the reason may be encode AVCodecContext args. I try to copy those args frome decode AVCodecContext, the output can be played by Win10 defualt player, but the video became totally black.
   Here is my encode AVCodecContext args :

          encoder = avcodec_find_encoder(AV_CODEC_ID_H264);
  
  
  
          if (!encoder) {
  
              av_log(NULL, AV_LOG_FATAL, "Necessary encoder not found\n");
  
              return AVERROR_INVALIDDATA;
  
          }
  
          enc_ctx = avcodec_alloc_context3(encoder);
  
          enc_ctx->height = output_height;
  
          enc_ctx->width = output_width;
  
          enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;
  
          enc_ctx->bit_rate = 1000000;
  
  
  
          /* take first format from list of supported formats */
  
          if (encoder->pix_fmts)
  
              enc_ctx->pix_fmt = AV_PIX_FMT_YUV420P;
  
          else
  
              enc_ctx->pix_fmt = dec_ctx->pix_fmt;
  
  
  
          enc_ctx->time_base = av_inv_q(dec_ctx->framerate);
  
          enc_ctx->gop_size = 12;
  
          av_opt_set(enc_ctx->priv_data, "preset", "slow", 0);
  
          av_opt_set(enc_ctx->priv_data, "tune", "zerolatency", 0);
  
  
  
          enc_ctx->profile = FF_PROFILE_H264_HIGH;
  
          enc_ctx->codec_type = AVMEDIA_TYPE_VIDEO;       
  
  
  
          enc_ctx->codec_tag = 0;

• FFMPEG conversion from .H264 to MP4 playing too fast

  28 juin 2017, par NickR

  I accidentally deleted a video file but managed to save it with a recovery tool. The video was however corrupted, but I managed to repair that and now have a .h264 file.

  The file plays ok in the VLC player. There are a few glitches but on the whole its 98% perfect. However I now need to convert that into a more useable format (mp4 say).

  Ive downloaded the FFMPEG tool and have managed to pretty easily copy into mp4 with the following command line instruction :

  ffmpeg -i repairedVid.h264 -c copy repairedVid.mp4

  The problem is that the video is playing much too fast. I’ve done some research tried some tweaks that seem to have worked for other people (like forcing frame rate and changing the -vsync) :

  ffmpeg -i repairedVid.h264 -c copy repairedVid.mp4 -vsync 2 -r 23.976

  Ive also tried the crude approach of slowing the video down like this, but this was more of a long shot and I don’t think is the right way to go about it

  ffmpeg -i repairedVid.mp4 -filter:v "setpts=1.5*PTS" repairedVid.mp4

  This is the output when the video copies to MP4. Looks like it might have a clue to the problem (the video should be much longer than 4:40 minutes) :

  frame=13459 fps=1118 q=-1.0 size= 4102773kB time=00:04:40.65 bitrate=119756.4kbiframe=13459 fps=1117 q=-1.0 Lsize= 4102928kB time=00:04:40.65 bitrate=119761.0kbits/s speed=23.3x
  video:4102773kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead : 0.003784%

  I’m totally new to FFMPEG and not having much luck. Any advice would be great.

  Thanks in advance

• Playing video with transparency in iOS

  14 juillet 2020, par 0Ds0

  A bit of background, i want to play videos with transparency on the web converted from gifs, for all non apple devices i can easily export a webm file like so

  


  ffmpeg -i test.gif -c:v libvpx-vp9 -qmin 0 -qmax 18 -crf 9 -b:v 1400K -quality good -cpu-used 0 -auto-alt-ref 0 -pix_fmt yuva420p -an -sn  -metadata title="test webm" test.webm

  


  No need for video streaming with HTTP response 206 partial content loaded it works out of the box

  


  Now for safari and apple devices i am presented with a totally different beast i set up a endpoint that serves the video with HTTP 206 responses and after a quite a struggle i can have the same end result for Safari in macOSX, and i convert the videos like so

  


  ffmpeg -i test.gif -qmin 0 -qmax 18  -vcodec prores_ks -q:v 64 -b:v 1400K  -pix_fmt yuva444p10le -profile:v 4444 -an -sn -metadata title="test mov" test.mov

  


  I put in the url address bar the that serves the video with stream and the video plays with transparency all good.

  


  Now on Safari in iOS the video just does not play, it is loaded with the same endpoint and other videos without transparency also work, serving from the same stream endpoint.

  


  Does anyone knows of a solution to encode a video with transparency that plays on all apple devices ?

  


  I also gave handbrake a try without success, actually could not even get the transparency right with handbrake.