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• Write seekable AAC audio stream into MP4 file with FFMPEG

  18 avril 2016, par lex82

  I’m trying to write an AAC audio stream into an mp4 file using the FFMPEG libraries. I am using a custom IO context that writes directly to a socket so I have to set ioContext->seekable = 0. To make this work I had to add the "movflags" empty_moov and frag_keyframe when writing the header.

  After writing the output to a file on the other end of the socket, I can play the file in VLC or Windows Media Player. However, seeking to a specific position in the file is not working properly in both players. WMP also does not show the total duration and VLC only flashes it shortly when reaching the end of the audio.

  Is there a way to add more metadata when muxing so the players are able to treat the file as if it was not written as a stream ? Transfer via the socket is not interrupted abruptly, so I could write metadata at the end of the file. I also know the total duration in advance, so I could add it to the header of the file if it was possible. I cannot use the faststart flag because this would require output to a seekable file before writing to the socket.

  Update : I learned that I can set the duration in AVFormatContext and I can set nb_frames and avg_frame_rate in AVStream. However, it doesn’t solve my problem. When I set the codecContext flag AV_CODEC_FLAG_QSCALE, VLC seems to be able to estimate the total time. However, seeking still doesn’t work.

• Data from Python to FFMpeg

  3 mai 2016, par user2956849

  I’m using Python and FFMpeg under Windows OS.

  The problem is to create a single video file from images and audio tracks, stored in memory as numpy array.

  I have done it in 2 steps, but I think it can be done better and faster :

  Firstly, i create video file (using pipe:0 to transfer data from python to FFMpeg)

  ffmpeg -y -f rawvideo -vcodec rawvideo -s 1920x1080 -pix_fmt bgr24 -r 5.00 -i pipe:0 -an -vcodec libx264 -preset medium -pix_fmt yuv420p video.avi

  Then from this file and audio track from pipe I create needed file :

  ffmpeg -y -f s16le -acodec pcm_s16le -ar 44100 -ac 1 -i pipe:0 -i video.avi -c:v h264 -c:a ac3 videoANDaudio.avi

  Is it possible to do it just in one FFMpeg call ? Can I use 2 pipe streams to transfer data ? I also tried named pipe, but I found nothing in Google.

  PS. May be there is any better way to do this ?

• Piping from ffmpeg to x264 not working

  23 mai 2016, par JiZhaku_San

  I want to encode video file to AVC-I50. I have a vbs script.

  set objShell = WScript.CreateObject ("WScript.Shell")
  
  
  
  objShell.run "cmd.exe /C Processors\ffmpeg.exe -i  """ & PathToInputFile & """ -f lavfi 
  
  -i aevalsrc=0 -loglevel quiet -shortest -filter_complex 
  
  ""[0:1]pan=1|c0=c0[a1],[0:1]pan=1|c0=c1[a2],[0:1]pan=1|c0=c2[a3],[0:1]pan=1|c0=c3[a4]""  
  
  -map ""[a1]"" -c:a pcm_s24le -ar 48000 -y -t """ & duration & """ tmp\01.wav 
  
  -map ""[a2]"" -c:a pcm_s24le -ar 48000 -y -t """ & duration & """ tmp\02.wav 
  
  -map ""[a3]"" -c:a pcm_s24le -ar 48000 -y -t """ & duration & """ tmp\03.wav 
  
  -map ""[a4]"" -c:a pcm_s24le -ar 48000 -y -t """ & duration & """ tmp\04.wav  
  
  -map 0:v -c:v rawvideo -strict -1 -vf format=yuv420p10,fps=fps=30000/1001 
  
  -s 1440x1080 -q:v 0 -an -f yuv4mpegpipe pipe:output.y4m | Processors\x264.exe - 
  
  --demuxer y4m  --frames 1077 --interlaced --tff  --output-csp i420 --no-cabac 
  
  --force-cfr --keyint 1 --colorprim bt709 --transfer bt709 --tune psnr --sar 1:1 
  
  --nal-hrd cbr --pic-struct --videoformat component  --vbv-maxrate 50000 --vbv-bufsize 2000 
  
  --colormatrix bt709 --bitrate 50000 --avcintra-class 50 --output tmp\Result.h264 ", 1, true

  When I try to run in cmd this vbs file, it is working.
  But when I try to run it in C# as Process - it doesn’t.
  Btw. when I try to run it as plain command in cmd it sais that
  "-" is not an input for x264.