On Thu, Feb 9, 2023 at 12:08 PM Martin Storsjö <mar...@martin.st> wrote:
>
> This looks reasonable to me. I didn't follow the references in the commit
> message, but it sounds plausible and probably correct to me.
>
For the record, due to dumb ISO/IEC rule changes regarding how
specifications need to be authorized to be free after 2015, it's
relatively hard to verify the 14496-12 part.
The last version of 14496-12 that was freely available (2015) defined
channelcount in AudioSampleEntry as follows:
template unsigned int(16) channelcount = 2;
Meanwhile the latest 2022 edition defines the related structure(s) as follows:
class AudioSampleEntry(codingname) extends SampleEntry (codingname) {
const unsigned int(32)[2] reserved = 0;
unsigned int(16) channelcount;
template unsigned int(16) samplesize = 16;
unsigned int(16) pre_defined = 0;
const unsigned int(16) reserved = 0 ;
template unsigned int(32) samplerate = { default samplerate of media} << 16;
// optional boxes follow
Box (); // further boxes as needed
ChannelLayout();
DownMixInstructions() [];
DRCCoefficientsBasic() [];
DRCInstructionsBasic() [];
DRCCoefficientsUniDRC() [];
DRCInstructionsUniDRC() [];
// we permit only one DRC Extension box:
UniDrcConfigExtension();
// optional boxes follow
SamplingRateBox();
ChannelLayout();
}
aligned(8) class SamplingRateBox extends FullBox('srat') {
unsigned int(32) sampling_rate;
}
class AudioSampleEntryV1(codingname) extends SampleEntry (codingname) {
unsigned int(16) entry_version; // shall be 1,
// and shall be in an stsd with version ==1
const unsigned int(16)[3] reserved = 0;
template unsigned int(16) channelcount; // shall 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();
Box (); // further boxes as needed
ChannelLayout();
DownMixInstructions() [];
DRCCoefficientsBasic() [];
DRCInstructionsBasic() [];
DRCCoefficientsUniDRC() [];
DRCInstructionsUniDRC() [];
// we permit only one DRC Extension box:
UniDrcConfigExtension();
// optional boxes follow
ChannelLayout();
}
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