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• Converting HLS video with fmp4 segments to image thumbnails via ffmpeg with start offset using fast seek

  19 octobre 2022, par hellerahum

  I'm having trouble with what I think should be a basic use case for ffmpeg. What I'd like to do is take an hls video in fmp4 and output 30s of images at 10fps, using "fast seek" to start at an offset well into the video. This works with an Apple sample using ts segments, but not with fmp4 segments.

  


  working sample (ts)

  


  ffmpeg -ss 00:00:05 -i https://devimages.apple.com.edgekey.net/iphone/samples/bipbop/bipbopall.m3u8 -t 30 -vf fps=10 hls_samples/img%03d.jpg


  


  broken sample (fmp4)

  


  ffmpeg -ss 00:00:05 -i https://devstreaming-cdn.apple.com/videos/streaming/examples/img_bipbop_adv_example_fmp4/master.m3u8 -t 30 -vf fps=10 hls_samples/img%03d.jpg


  


  The broken sample spits out errors like :

  


  [NULL @ 0x123e30d20] Invalid NAL unit size (-2003396084 > 1673).
[NULL @ 0x123e30d20] missing picture in access unit with size 1677


  


  and then finally :

  


  Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)
Conversion failed!


  


  When I re-encode the fmp4 video adding keyframes via -g 1 (still hls with fmp4) I'm then able to use the fast seek -ss flag before the -i , but i'd rather not do this in a 2-step process, and ideally would take the original hls/fmp4 manifest and output the thumbnails directly. Both samples work with the -ss flag after the input (slow seek) but I have some long (10+ hour) videos so that's not tenable. Anyone able to point me to what I'm doing wrong, or is it possible this is an issue with ffmpeg and its support for fmp4 ? I'm using ffmpeg v5.1.2 and have checked on both an M1 mac and Ubuntu system.

  


• checkasm : aacencdsp : Actually test nonzero values in quant_bands

  29 janvier, par Martin Storsjö

  checkasm : aacencdsp : Actually test nonzero values in quant_bands
  Previously, we read elements from ff_aac_pow34sf_tab ; however
  
  that table is initialized to zero ; one needs to call
  
  ff_aac_float_common_init() to make sure that the table is
  
  initialized.
  However, given the range of the input values, a large number of
  
  entries in ff_aac_pow34sf_tab would give results outside of the
  
  range for signed 32 bit integers. As the largest aac_cb_maxval
  
  entry is 16, it seems more reasonable to produce values within
  
  an order of mangitude of that value.
  (When hitting INT_MIN, implementations may end up with different
  
  results depending on whether the value is negated as a float or
  
  as an int. This corner case is irrelevant in practice as this
  
  is way outside of the expected value range here.)
  Coincidentally, this fixes linking checkasm with Apple's older
  
  linker. (In Xcode 15, Apple switched to a new linker. The one in
  
  older toolchains seems to have a bug where it won't figure out to
  
  load object files from a static library, if the only symbol
  
  referenced in the object file is a "common" symbol, i.e. one for
  
  a zero-initialized variable. This issue can also be reproduced with
  
  newer Apple toolchains by passing -Wl,-ld_classic to the linker.)
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] tests/checkasm/aacencdsp.c

• Get 'location' of video using ffmpeg and regex

  6 février 2014, par Foysal

  I have a metadata text of a video file which is produced by ffmpeg.

  Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      creation_time   : 2011-09-10 21:44:22
  
      model           : iPhone 4
  
      model-deu       : iPhone 4
  
      encoder         : 4.3.5
  
      encoder-deu     : 4.3.5
  
      date            : 2011-09-10T17:44:22-0400
  
      date-deu        : 2011-09-10T17:44:22-0400
  
      location        : +40.7329-073.9864/
  
      location-deu    : +40.7329-073.9864/
  
      make            : Apple
  
      make-deu        : Apple

  What regex i need to write if I want to get the 'location' value from above text. I am using C#.