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mp4a: Support DecoderSpecificDescriptor profiles > 30

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Adds support for reading and writing AAC audio specific info when
profile (object type) is larger than 30.
This commit is contained in:
Peter Zebühr 2023-10-17 14:44:16 +07:00
parent 32674a6855
commit 0a3973b827
1 changed files with 60 additions and 5 deletions
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65
src/mp4box/mp4a.rs
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@ -507,14 +507,18 @@ impl Descriptor for DecoderSpecificDescriptor {
}
fn desc_size(&self) -> u32 {
2
if self.profile < 31 {
2
} else {
3
}
}
}
fn get_audio_object_type(byte_a: u8, byte_b: u8) -> u8 {
let mut profile = byte_a >> 3;
if profile == 31 {
profile = 32 + ((byte_a & 7) | (byte_b >> 5));
profile = 32 + ((byte_a & 7) << 3 | (byte_b >> 5));
}
profile
@ -533,7 +537,7 @@ fn get_chan_conf<R: Read + Seek>(
chan_conf = ((sample_rate >> 4) & 0x0F) as u8;
} else if extended_profile {
let byte_c = reader.read_u8()?;
chan_conf = (byte_b & 1) | (byte_c & 0xE0);
chan_conf = (byte_b & 1) << 3 | (byte_c >> 5);
} else {
chan_conf = (byte_b >> 3) & 0x0F;
}
@ -569,8 +573,15 @@ impl<W: Write> WriteDesc<&mut W> for DecoderSpecificDescriptor {
let size = self.desc_size();
write_desc(writer, Self::desc_tag(), size)?;
writer.write_u8((self.profile << 3) + (self.freq_index >> 1))?;
writer.write_u8((self.freq_index << 7) + (self.chan_conf << 3))?;
if self.profile < 31 {
writer.write_u8((self.profile << 3) | (self.freq_index >> 1))?;
writer.write_u8((self.freq_index << 7) | (self.chan_conf << 3))?;
} else {
let profile_minus_32 = self.profile - 32;
writer.write_u8(31u8 << 3 | profile_minus_32 >> 3)?;
writer.write_u8(profile_minus_32 << 5 | self.freq_index << 1 | self.chan_conf >> 7)?;
writer.write_u8((self.chan_conf & 7) << 5)?;
}
Ok(size)
}
@ -682,4 +693,48 @@ mod tests {
let dst_box = Mp4aBox::read_box(&mut reader, header.size).unwrap();
assert_eq!(src_box, dst_box);
}
#[test]
fn test_decoder_specific_descriptor() {
let test_dec_spec = |src_dec_spec: DecoderSpecificDescriptor| {
let mut buf = Vec::new();
let written = src_dec_spec.write_desc(&mut buf).unwrap();
// expect two extra bytes for the tag and size fields
assert_eq!(buf.len(), written as usize + 2);
let mut reader = Cursor::new(&buf);
let (tag, size) = read_desc(&mut reader).unwrap();
assert_eq!(5, tag);
assert_eq!(size, written);
let dst_dec_spec = DecoderSpecificDescriptor::read_desc(&mut reader, written).unwrap();
assert_eq!(src_dec_spec, dst_dec_spec);
};
test_dec_spec(DecoderSpecificDescriptor {
profile: 2, // LC
freq_index: 4, // 44100
chan_conf: 2, // Stereo
});
test_dec_spec(DecoderSpecificDescriptor {
profile: 5, // SpectralBandReplication (HEv1)
freq_index: 3, // 48000
chan_conf: 1, // Mono
});
test_dec_spec(DecoderSpecificDescriptor {
profile: 29, // ParametricStereo (HEv2)
freq_index: 2, // 64000
chan_conf: 7, // SevenOne
});
test_dec_spec(DecoderSpecificDescriptor {
profile: 34, // MpegLayer3
freq_index: 4, // 44100
chan_conf: 2, // Stereo
});
test_dec_spec(DecoderSpecificDescriptor {
profile: 42, // UnifiedSpeechAudioCoding (xHE)
freq_index: 11, // 8000
chan_conf: 6, // FiveOne
});
}
}