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• FFmpeg reverse long audio hang randomly in Android

  23 mars 2021, par Michael

  I am writing an Android APP, underneath I simply use FFmpeg command to reverse the audio.

  


  The command is simple like :ffmpeg -loglevel debug -debug_ts -i /sdcard/.m4a -af areverse /sdcard/longaudio.aac

  


  If the audio is short, everything works fine, but if the audio longer than 10 mins, the thread will hang(sleep) randomly at some places. The log shows input processing stop in middle at some pkt_pts, every time stop at different ptk_pts. The whole app will therefore hang in there.

  


  If I simply do conversion "ffmpeg -loglevel debug -debug_ts -i /sdcard/.m4a -codec:a aac /sdcard/longaudio.aac" it will work.

  


  Some debug steps I did :

  


  


  1. The memory and cpu usage is normal, it seems the ffmpeg just suddenly decide to take a rest during reverse the long audio :(

     


  


  2. the IO shouldn't be fulled, I commented out the logs still not ok.

     


  


  3. I see a lot "cur_dts is invalid (this is harmless if it occurs once at the start per stream)", but it also showed in normal cases.

     


  


  


  I know the description is kind of ambiguous, but I am so desperate. Anything I don't know about the audio reverse is welcome.

  


• How to generate a video by looping an image and then concat with another very long video without re-encoding using ffmpeg ?

  23 mars 2021, par Linghao Chen

  I have an image and a very long video (1.5h).
Now I want to generate a heading video about 5 seconds by looping the image, and then concatenate it with the long video. Since the video is long, I don't want to re-encode the videos.
I have tried to generate the heading video using

  


  ffmpeg -loop 1 -i image.png -c:v libx264 -t 5 -pix_fmt yuv420p head.mp4


  


  and then

  


  ffmpeg -f concat -i list.txt -c:v copy concat.mp4


  


  where the list.txt contains

  


  file head.mp4
file longvideo.mp4


  


  I have tried these operations on two machines.
On one machine, the concatenated video has no audio. Moreover, it stucks at 5-10 seconds and directly jump to 11s.
On the other machine, the video and audio are not synchronized.

  


  To provide more information, I have checked the codecs of the two videos by

  


  ffprobe -v error -select_streams v:0 -show_entries stream=codec_name \
  -of default=noprint_wrappers=1:nokey=1 xxxxx.mp4


  


  Both of them are h264.

  


  My question is, how to generate it correctly with ffmpeg ? If it is hard using ffmpeg, is there any method to do it fast ? As far as I know, Adobe Premiere and Final Cut Pro do not export as fast as I expect because they re-encode the videos.

  


• avformat/avlanguage : Remove long disabled av_convert_lang_to

  25 février 2021, par Andreas Rheinhardt

  avformat/avlanguage : Remove long disabled av_convert_lang_to
  1582e306a47977b09fddb029b999f99eb03cd485 scheduled it for removal with
  
  libavformat major version 58, but it was never removed.
  Reviewed-by : Paul B Mahol <onemda@gmail.com
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/avlanguage.c
  • [DH] libavformat/avlanguage.h