[FFmpeg-trac] #6609(ffmpeg:new): SamplingRateBox should be used if the value is greater than INT16_MAX

[FFmpeg]

#6609: SamplingRateBox should be used if the value is greater than INT16_MAX
-------------------------------------+-------------------------------------
             Reporter:  fbeaufort    |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  ffmpeg
              Version:  unspecified  |               Resolution:
             Keywords:  flac,        |               Blocked By:
  isobmff, mp4                       |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Changes (by jyavenard):

 * keywords:  mov => flac, isobmff, mp4
 * component:  avformat => ffmpeg


Comment:

 As present, ffmpeg if MODE_MOV is set, and a sampling rate greater thant
 UINT16_MAX, can generate a .mov with SoundDescription that would be using
 a 64 bits float for sampling rate.

 For a mp4 (as defined in ISO 14496-12 12.2.3.2), it should be using a
 AudioSampleEntryV1 defined as follow:

 {{{
 class AudioSampleEntryV1(codingname) extends SampleEntry (codingname){
    unsigned int(16) entry_version;  // must be 1,
                               //   and   must   be   in   an   stsd   with
 version   ==1
    const unsigned int(16)[3] reserved = 0;
    template unsigned int(16) channelcount;  // must be correct
    template unsigned int(16) samplesize = 16;
    unsigned int(16) pre_defined = 0;
    const unsigned int(16) reserved = 0 ;
    template unsigned int(32) samplerate = 1<<16;
    // optional boxes follow
    SamplingRateBox();
    ChannelLayout();
    // we permit any number of DownMix or DRC boxes:
    DownMixInstructions()   [];
    DRCCoefficientsBasic()   [];
    DRCInstructionsBasic()   [];
    DRCCoefficientsUniDRC()   [];
    DRCInstructionsUniDRC()   [];
    Box ();     // further boxes as needed
 }
 }}}

 The samplerate would then be 65536 and there would be a SamplingRateBox
 {{{
 aligned(8) class SamplingRateBox extends FullBox(‘srat’) {
    unsigned int(32) sampling_rate;
 }
 }}}

 FFmpeg when generating a mp4 and if the sampling rate is greater than
 65535, always write 0 as the sampling rate.
 see
 https://github.com/FFmpeg/FFmpeg/blame/5f4e555dc7caea343838e9f6f218525bb80216bf/libavformat/movenc.c#L974

 Expected:
 It should instead use a AudioSampleEntryV1 and a SamplingRateBox (srat)

 For related bug, I've lodged gecko's bug 1393045
 (https://bugzilla.mozilla.org/show_bug.cgi?id=1393045) and bug 1393039
 (https://bugzilla.mozilla.org/show_bug.cgi?id=1393039)

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6609#comment:2>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker