Recherche avancée

Sur d’autres sites (7062)

• How To Get FFMPEG To Continuously Overwrite/Append Audio File ?

  28 octobre 2018, par GPinskiy

  I installed an external audio card onto my Raspberry Pi 3 and I want to Chromecast the recorded audio. I have set up a Node.js server to cast things and have set up the sound card using alsamixer. I can correctly hear the line-in on the headphones when I use the command arecord -D hw:0,0 -r 48000 -f S32_LE -c 2 | aplay -D dmix:CARD=audioinjectorpi,DEV=0 -r 48000 -f S32_LE -c 2 to simulate pass-through.

  The last step is to actually expose this stream in a way that the Chromecast can access. The Chromecast can’t use a RDP stream or anything similar, only files. So I thought that I could get away with having FFMPEG create an mp3 file that it continuously appends to while dropping the last x seconds so that the overall length of the mp3 file is only like 20 seconds and having a local web server that the Chromecast can get that file from.

  I see that there is a way to automatically segment in FFMPEG but that create a bunch of separate 20 sec files rather than a single file that is 20 secs. What would be the correct way of doing this ?

• Timing breaks concatenating two identical videos after one has ATEMP/SETPTS altered

  25 mai 2019, par user3144514

  Video (B)
  Copy pasted and then doubled speed with Setpts and Atempo as Video (A)

  Concatenating them results in a video with the (A) portion playing at the expected 2x speed, but the (B) portion playing back at 1/2 speed.

  I am simply trying to speed up sections of video that are repetative and merge them back in.

  I have tried doing another round of SETPTS/ATEMPO with 1.0 values, but it doesn’t alter the outcome.

  I have also tried forcibly re-encoding A and B to ensure they match in formats, still no change.

  Speed Change

  ffmpeg -i source.mp4 -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" A.mp4

  Concatenation

  ffmpeg -i A.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts x1.ts
  
  ffmpeg -i B.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts x2.ts
  
  ffmpeg -i "concat:x1.ts|x2.ts" -c copy -bsf:a aac_adtstoasc C.mp4

  Do I need to use some other method to alter the playback rate without changing some internal timing value ?

  Or is there some way to fix the rates after adjusting SETPTS and ATEMPO so that the timing is restored ?

• combine specific mpeg-dash segments (ex int.mp4 + seg_1.m4s +seg_3.m4s) into one single mp4 file

  16 avril 2019, par Liquid

  I am working one video transcoding in FFmpeg and MP4Box. Currently I am trying to combine/merge/concatenate specific MPEG-DASH video segments(m4s ex:int.mp4, seg_1.m4s, seg2,m4s,sge5.m4s) into one mp4 file.

  This the example of what I am trying to do.

  I have followed this thread ("Combine MPEG-DASH segments (ex, init.mp4 + segments.m4s) back to a full source.mp4 ?") but there is a problem while combining the specific m4s segments, while doing that it frames feazed in after seg2 and in seg5 it played again.

  Reference : FFmpeg example