Recherche avancée

Sur d’autres sites (6951)

• FFMPEG - Creating multiple copies of a video with different audio channels. Can't hear channel 4

  13 février 2020, par Gabriel_ris

  I’m working on a project where I need to have 6 copies of a video, where each copy only plays one audio channel.
  The original video has only 2 channel, with the same audio on each channel.
  First I had to copy one of the channels into the other 4 missing channels.
  I’m new to ffmpeg, I did some research and I used this command :

  ffmpeg -i input.mp4 -map_channel 0.1.0 -map_channel 0.1.0 -map_channel
  0.1.0 -map_channel 0.1.0 -map_channel 0.1.0 -map_channel 0.1.0 -c:v copy output.mp4

  That helped to turn the video into a 6 channels one. Then, I revised the command for each channel :

  ffmpeg -i input.mp4 -map_channel 0.1.0 -map_channel -1 -map_channel -1
  -map_channel -1 -map_channel -1 -map_channel -1 -c:v copy output_channel1.mp4

  ffmpeg -i input.mp4 -map_channel -1 -map_channel 0.1.0 -map_channel -1
  -map_channel -1 -map_channel -1 -map_channel -1 -c:v copy output_channel2.mp4

  and so on.

  All the videos worked perfectly on their own channels, but channel 4, in which I can only hear some low noise.
  I read channel 4 is used for low frequency audio in 5.1 configuration, which might be the problem.
  I tried specifying the channel layout to 6.0, increasing the volume, disabling guess_layout_max, but nothing worked.
  As I said, I’m new to ffmpeg, and probably there is a much better way to do it. I’d appreciate if someone here could help me.
  Thanks !

• Some Java Process objects finish and close, but some finish and stall

  28 mars 2020, par brendanw36

  My program uses ProcessBuilder to make various calls to ffmpeg. My problem is that with certain commands I can create a Process, have it run, and when it is done it will terminate/exit/close itself and the program will end whereas other commands will run and create a finished output (in my case it will finish encoding a file with no corruption or anything at the end of the video), but won’t close at which point I need to force terminate the program. I have tested the ffmpeg commands that I am running in Windows Command Prompt and they all run fine without need for user input or anything. I will show some examples of commands that do and don’t work, but ultimately what I need is a way to tell why certain Processes do and don’t work. You probably don’t even need to read the rest of this post if you know the inner workings of the Process class better than I do.

  How I create my processes :

  ProcessBuilder pb = new ProcessBuilder(commandGoesHere);
  
  Process p = pb.start();
  
  p.waitFor();

  Works :
  ffmpeg -i test.y4m -f segment -segment_times timecodeList .temp/sgmnt_%d.y4m

  This command takes a y4m(raw video format/large file size/1.7 GB for 53s of 720p video) and cuts it in to chunks.

  Doesn’t work (sometimes) :
  ffmpeg -i chunkname.y4m outputName.mkv

  This command takes the chunked video and encodes it as h.264/AVC video. When I create a process with this command it only works if the chunk is small in which case the Process will start, do its work, and close.

  Doesn’t work ever :
  ffmpeg -i test.mkv -c:v copy -f segment -segment_times timecodeList .temp/sgmnt_%d.mkv

  This command takes and h.264/AVC input video and cut it in to chunks, but this one doesn’t terminate/exit/close when it’s done. I’m forced to terminate the program which I do after seeing the Process’s CPU utilization drop to 0% in Task Manager. When I force terminate the program and check the output folder, all the chunks are there and not corrupted so I know it finished running successfully.

• Why Do Some of the Codecs in FFMPEG's Supported Codec List Show "encoders :" or "decoders :" in Parenthesis ?

  4 mai 2020, par spaceman

  If you open the Command Prompt, and run ffmpeg -codecs,
  
you will get a long list of Codecs that FFMPEG supports.

  



  Here's a small sample of the list :

  



   DEV.L. h261                 H.261
 DEV.L. h263                 H.263 / H.263-1996, H.263+ / H.263-1998 / H.263 version 2
 D.V.L. h263i                Intel H.263
 DEV.L. h263p                H.263+ / H.263-1998 / H.263 version 2
 DEV.LS h264                 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (encoders: libx264 libx264rgb)
 D.V.LS hevc                 H.265 / HEVC


  



  Now If you briefly go over the whole list,
  
you see that most Codecs in this list appear with their Name and Description,
  
but some of the Codecs also include parenthesis in the Description, and in the parenthesis,
  
they specify "encoders :" or "decoders :".

  



  For example :

  



  1)

  



   DEV.LS h264                 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (encoders: libx264 libx264rgb)


  



  2)

  



   DEVILS jpeg2000             JPEG 2000 (decoders: jpeg2000 libopenjpeg) (encoders: jpeg2000 libopenjpeg)


  



  3)

  



   DEV.L. msmpeg4v3            MPEG-4 part 2 Microsoft variant version 3 (decoders: msmpeg4) (encoders: msmpeg4)


  



  4)

  



   DEA.L. aac                  AAC (Advanced Audio Coding) (encoders: aac libvo_aacenc)


  



  5)

  



   DEA.L. amr_nb               AMR-NB (Adaptive Multi-Rate NarrowBand) (decoders: amrnb libopencore_amrnb) (encoders: libopencore_amrnb)
 DEA.L. amr_wb               AMR-WB (Adaptive Multi-Rate WideBand) (decoders: amrwb libopencore_amrwb) (encoders: libvo_amrwbenc)


  



  My question :

  



  Why do some Codecs have those parenthesis, specifying Encoders/Decoders,
  
while other (in fact : most) codecs don't have these parenthesis ?