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• Best video format using ffmpeg converter

  2 août 2016, par nodeffect

  I’m making a website that is something like "youtube" which allows people to upload their videos and then playback within that site.

  I’m using Videojs for the video playback and I’m trying to use ffmpeg for converting their videos to a smaller file size but remain almost the same quality as the original.

  For now, I’m not sure which format should I choose from. I tried mp4 and webm and sometimes the file size after I convert to mp4 is smaller than webm but, it is also sometimes larger than the original file size. I don’t know which is the best format in terms of file size and quality. I’m hoping to convert any video file to a smaller file size.

  The command that I’m using now is "ffmpeg -i test.mov test.mp4" and "ffmpeg -i test.avi test.webm"

  Anyone could recommend me the best one ? In terms of file size and also the quality. Thanks

• FFMPEG increases bitrate after splitting an avi file

  30 mai 2018, par Yaser Sakkaf

  I am trying to split a video (.avi) file with duration of 1 hour to 8 minutes.
  I am using the following command

   ffmpeg -i videos_22_05_18/cnbc.avi -ss 00:00:00 -to 00:08:00 -c copy 1.avi

  But it makes a video of 37 minutes instead and also the audio quality is too fast.

  I compared the specifications of the original .avi file and the resulting one, and the only difference is that of bitrate.

  Bitrate of original file is 646k while that of splitted file is 1126.

  I have literally tried every thing.
  like using

  ffmpeg -i videos_22_05_18/cnbc.avi -ss 00:00:00 -to 00:08:00 -c copy -b 646k 1.avi

  AND

  ffmpeg -i videos_22_05_18/cnbc.avi -ss 00:00:00 -to 00:08:00 -c copy -async 1 1.avi

  AND

  ffmpeg -i videos_22_05_18/cnbc.avi -ss 00:00:00 -to 00:08:00 -c copy -b 646k -async 1 1.avi

  AND

  ffmpeg -i videos_22_05_18/cnbc.avi -ss 00:00:00 -to 00:08:00 -vcodec copy -acodec copy -b 646k 1.avi

  AND
  MANY MORE combinations

  Nothing seems to work
  I don’t know why it is happening like this. PLease help.

• ffmpeg HLS stream audio is out of sync when input video are multiple clips joined using AVComposition

  11 décembre 2019, par Tomáš Kohout

  I am having problems with HLS stream creation that seems to be either on FFMPEG or iOS AVFoundation side.

  I am currently working on a video app which allows user to record, cut and merge multiple clips together. That is done using AVMutableComposition and code like this :

  try videoTrack?.insertTimeRange(clip.range, of: videoAssetTrack, at: accumulatedTime)
  
  try audioTrack?.insertTimeRange(clip.range, of: audioAssetTrack, at: accumulatedTime)

  and then it gets exported using

  AVAssetExportSession(asset: composition, presetName: preferredPreset)

  Then it gets uploaded to a server which creates a HLS stream out of the video using following code :

  ffmpeg -i bunny.mov -y -g 48 -sc_threshold 0 \
  
  -map 0:0 -map 0:1 -s:v:0 1280x720 -c:v:0 h264 -b:v:0 4000k \
  
  -map 0:0 -map 0:1 -s:v:1 854x480 -c:v:1 h264 -b:v:1 2000k \
  
  -map 0:0 -map 0:1 -s:v:2 640x360 -c:v:2 h264 -b:v:2 1000k \
  
  -map 0:0 -map 0:1 -s:v:3 480x270 -c:v:3 h264 -b:v:3 500k \
  
  -c:a copy -var_stream_map "v:0,a:0 v:1,a:1 v:2,a:2 v:3,a:3" \
  
  -master_pl_name bunny.m3u8 -f hls -hls_time 1 -hls_list_size 0 \
  
  -hls_segment_filename ~/Downloads/bunny/bunny.%v.%03d.ts \
  
  -hls_base_url http://tomaskohout.cz/bunny/ ~/Downloads/bunny/bunny.%v.m3u8

  Inputting a video that was cut together using two clips (first a bird and second a bunny) will result in following m3u8 file (open in safari to see it play) : http://tomaskohout.cz/bunny/bunny.m3u8

  The problem is that the audio is overlapping and out of sync after the first cut (notice the sound of nut hitting the bird playing twice) and last second is just a still frame.

  The original video for comparison is here :
  http://tomaskohout.cz/bunny/original.mov

  Seems like it is a problem in AVFoundation in general. If you join two clips using QuickTime (with Edit > Add Clip to End) and use the resulting video as the input for ffmpeg it will also have audio and video out of sync. It just seems it generates some strangely timed videos that only quicktime knows how to play. If you take the original video and try to play it using VLC it will be also out of sync and even show part of the clip that were not meant to be in the original cut. It might be related to the Encoder Delay and Synchronization but I am really out of my element here.

  I have found a workaround which is to first convert the video to mp4 (in my case it’s just converting mp4 to mp4) like this :

  ffmpeg -i input.mp4 -c:v:0 h264 input.preexport.mp4

  and then use the pre-exported version to generate the m3u8 file. This seems to retime the video correctly.

  That is of course not ideal because I have to run through the video twice.

  So I would like to ask whether there’s either an option which allows me to retime the video at the same time while I am generating the hls or even better if there is some other solution to the problem.

  Thank you !

  Tomas