Recherche avancée

Sur d’autres sites (7972)

• Does ffmpeg pass a file through if it already conforms to the given transmux options ?

  8 janvier 2021, par anonymous coward

  Assuming I have an MP3 file with this qualities :

  


  

  • mono

  


  • 44100 sample rate

  


  • 64k constant bitrate

  


  


  Question : If I provide that file to ffmpeg as input, using the command line arguments necessary to transmux it to an output file matching the aforementioned values, which of the following should I expect from the output result ? :

  


  

  • A worse quality version of the original file, because it's be re-compressed in a lossy way.

  


  • The same file, because ffmpeg didn't need to do anything.

  


  • Something else entirely...?

  


  


  ---

  


  Extra context :

  


  I'd like to batch transmux a set of provided audio files. But there's a chance that some of those files already conform to a given standard.

  


  I'm wondering if I need to check for those maximum values before handing the file to ffmpeg (to avoid unnecessary processing) or if that would be wasteful because ffmpeg is smart enough to handle that case ?

  


• How to get frame information from fragmented mp4

  17 novembre 2020, par Duke Atista

  I'm using the following command to generate fmp4 files

  


  ffmpeg -rtsp_transport tcp -i rtsp://someuser:somepassword@somedomain:someport/Streaming/Channels/101 -acodec copy -vcodec copy -hls_segment_type fmp4 -hls_time 2 -hls_list_size 10 -hls_flags delete_segments+append_list+split_by_time -hls_playlist_type event test.m3u8

  


  I need to know the exact duration and frame count of each fragment. Unfortunately -vstats appears to be ignored.

  


  I tried to probe one of the segments using

  


  ffprobe -show_frames ./test0.m4s

  


  But I get

  


  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fb68e80b000] could not find corresponding track id 1 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fb68e80b000] could not find corresponding trex (id 1) [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fb68e80b000] could not find corresponding track id 0 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fb68e80b000] trun track id unknown, no tfhd was found [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fb68e80b000] error reading header ./test0.m4s: Invalid data found when processing input

  


  I'm assuming that is because the initialisation segment has not been loaded but I can't find the option to do so.

  


  If I try probing the initialisation segment with

  


  ffprobe -show_frames ./init.mp4

  


  I get no frame information and the error

  


  Could not find codec parameters for stream 0 (Video: h264 (avc1 / 0x31637661), none, 2560x1440): unspecified pixel format Consider increasing the value for the 'analyzeduration' and 'probesize' options

  


  Would appreciate any help.

  


• Create fragmented MP4 from MP3

  25 octobre 2020, par Stefan Falk

  I am trying to convert an MP3 file to a fragmented MP4 like this :

  


  ffmpeg -i input.mp3 -strict experimental -acodec aac -b:a 256k -f mp4 \
       -movflags faststart+frag_keyframe+empty_moov+separate_moof output.mp4 


  


  However, using Bento4 I can see that there is just one giant mdat object instead of a series of those :

  


  [ftyp] size=8+24
  major_brand = isom
  minor_version = 200
  compatible_brand = isom
  compatible_brand = iso2
  compatible_brand = iso6
  compatible_brand = mp41
[moov] size=8+701
  ...
[moof] size=8+62364
  ...
[mdat] size=8+5794679
[mfra] size=8+59
  [tfra] size=12+31, version=1
    track_ID = 1
    length_size_of_traf_num = 0
    length_size_of_trun_num = 0
    length_size_of_sample_num = 0
  [mfro] size=12+4
    mfra_size = 67


  


  I think what I want is this :

  


  

  


  (source)

  


  But I can't seem to be able to get this from ffmpeg.

  


  I found some other options here like

  


  $ ffmpeg -h muxer=ismv&#xA;...&#xA;-frag_duration     <int>   E.... Maximum fragment duration&#xA;-min_frag_duration <int>   E.... Minimum fragment duration&#xA;-frag_size         <int>   E.... Maximum fragment size&#xA;</int></int></int>

  


  but playing around with these didn't change the output.

  


  How can I create fragments of a specific sice e.g. 5 seconds each ?