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• Post processing in ffmpeg to move 'moov atom' in MP4 files (qt-faststart)

  12 septembre 2014, par siliconpi

  Is it possible to run ffmpeg from the command line which will either place the ’moov atom’ metadata in the beginning of the MP4 file or run the qt-faststart as a post processing operation in ffmpeg so the generated file is stream-able through the internet ?

  I can of course run it as a separate command, but would prefer it to be something

  • as an option within ffmpeg, or
  • as part of a post conversion, command line option when converting the video files via ffmpeg

  ---

  Edit 1

  http://ffmpeg.org/ffmpeg.html#mov

  MOV / MP4 muxer

  The muxer options are :

  ‘-moov_size bytes’

  Reserves space for the moov atom at the beginning of the file instead of 
  
  placing the moov atom at the end. If the space reserved is insufficient, 
  
  muxing will fail.

• How does the moov atom corrupt when editing metadata

  20 juin 2015, par Sam

  I have been editing metadata for some video files that I have, using a program called iDentify (on a mac). This is an old version of the program, made before they charged for it. It generally works perfectly, however about one in a hundred files that it processes, corrupts as it updates the metadata (artwork, description etc). The file is then un-openable.

  If I run the corrupt mp4 file through ffmpeg, I get an error saying that the moov atom could not be found. I have tried to research and I think the moov atom is sort of like a folder within the file, that holds the movie data... But I really am not sure about it. It seems like this is an issue that is normally seen when a camera crashes while filming, before it can make an index for the file. Thats not the case here, the file worked fine before running it through identify.

  What I would like to know is how editing the metadata can corrupt a file like this. Does anyone have any suggestions what the identify application would be doing to a file to corrupt it in this way ? The application is really quick (a couple of seconds), there is no encoding or new files, just inserting metadata.

  I managed to get another copy of the original good file and made a few copies of it. Every time I ran that particular video through identify, it would come out corrupted (but was absolutely fine beforehand). Therefore there must be a characteristic in the file that makes inserting metadata dangerous, causing corruption.

  Can anyone suggest what might be causing this corruption of the moov atom ? And then it might be possible to work out a fix...?

• How can I stream very long H.264 videos over HTTP without long startup times ? (or : MOOV atom too large)

  5 octobre 2012, par michael

  I want to stream videos of public meetings that are often 10 hours long. Users will generally be starting at some point in the middle of the video and jumping around frequently.

  H.264 in an MP4 container seems like the current best option for encoding streaming video (right ?). But these are large files — about 1.3GB for one file — and the metadata (MOOV atom) at the beginning of the file is itself about 40MB. If I understand correctly, clients need to download the full metadata before they're able to seek within the remainder of the file. Obviously, having to download 40MB before you can start streaming is unacceptable.

  (My tests of streaming have been with VLC and the HTML5 tag in Chrome.)

  I'm encoding the file using avconv, and am currently providing no additional settings beyond telling it which encoders to use (x264 and libfaac). I then move the metadata to the beginning of the file using qt-faststart.

  Is there a way to make the MOOV atom smaller ?

  If not, are there other strategies to use (e.g. is splitting long videos into several files something that's frequently done ? it seems like a real pain in terms of users seeking around the whole day's video) ?

  Or should I be using a different codec or container ?

  thanks !

  Here's a breakdown of the file header structure, from AtomicParsley :

  Atom ftyp @ 0 of size: 32, ends @ 32
  
  Atom moov @ 32 of size: 40157673, ends @ 40157705
  
       Atom mvhd @ 40 of size: 108, ends @ 148
  
       Atom iods @ 148 of size: 24, ends @ 172
  
       Atom trak @ 172 of size: 20156304, ends @ 20156476
  
           Atom tkhd @ 180 of size: 92, ends @ 272
  
           Atom edts @ 272 of size: 36, ends @ 308
  
               Atom elst @ 280 of size: 28, ends @ 308
  
           Atom mdia @ 308 of size: 20156168, ends @ 20156476
  
               Atom mdhd @ 316 of size: 32, ends @ 348
  
               Atom hdlr @ 348 of size: 45, ends @ 393
  
               Atom minf @ 393 of size: 20156083, ends @ 20156476
  
                   Atom vmhd @ 401 of size: 20, ends @ 421
  
                   Atom dinf @ 421 of size: 36, ends @ 457
  
                       Atom dref @ 429 of size: 28, ends @ 457
  
                   Atom stbl @ 457 of size: 20156019, ends @ 20156476
  
                       Atom stsd @ 465 of size: 147, ends @ 612
  
                           Atom avc1 @ 481 of size: 131, ends @ 612
  
                               Atom avcC @ 567 of size: 45, ends @ 612
  
                       Atom stts @ 612 of size: 6115608, ends @ 6116220
  
                       Atom stss @ 6116220 of size: 16960, ends @ 6133180
  
                       Atom ctts @ 6133180 of size: 5683824, ends @ 11817004
  
                       Atom stsc @ 11817004 of size: 28, ends @ 11817032
  
                       Atom stsz @ 11817032 of size: 4169724, ends @ 15986756
  
                       Atom stco @ 15986756 of size: 4169720, ends @ 20156476
  
       Atom trak @ 20156476 of size: 20001133, ends @ 40157609
  
           Atom tkhd @ 20156484 of size: 92, ends @ 20156576
  
           Atom mdia @ 20156576 of size: 20001033, ends @ 40157609
  
               Atom mdhd @ 20156584 of size: 32, ends @ 20156616
  
               Atom hdlr @ 20156616 of size: 45, ends @ 20156661
  
               Atom minf @ 20156661 of size: 20000948, ends @ 40157609
  
                   Atom smhd @ 20156669 of size: 16, ends @ 20156685
  
                   Atom dinf @ 20156685 of size: 36, ends @ 20156721
  
                       Atom dref @ 20156693 of size: 28, ends @ 20156721
  
                   Atom stbl @ 20156721 of size: 20000888, ends @ 40157609
  
                       Atom stsd @ 20156729 of size: 96, ends @ 20156825
  
                           Atom mp4a @ 20156745 of size: 80, ends @ 20156825
  
                               Atom esds @ 20156781 of size: 44, ends @ 20156825
  
                       Atom stts @ 20156825 of size: 9348168, ends @ 29504993
  
                       Atom stsc @ 29504993 of size: 28, ends @ 29505021
  
                       Atom stsz @ 29505021 of size: 5326296, ends @ 34831317
  
                       Atom stco @ 34831317 of size: 5326292, ends @ 40157609
  
       Atom udta @ 40157609 of size: 96, ends @ 40157705
  
           Atom meta @ 40157617 of size: 88, ends @ 40157705
  
               Atom hdlr @ 40157629 of size: 33, ends @ 40157662
  
               Atom ilst @ 40157662 of size: 43, ends @ 40157705
  
                   Atom ©too @ 40157670 of size: 35, ends @ 40157705
  
                       Atom data @ 40157678 of size: 27, ends @ 40157705
  
  Atom free @ 40157705 of size: 8, ends @ 40157713
  
  Atom mdat @ 40157713 of size: 1320096566, ends @ 1360254279