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Accept M4A files with invalid dependsOnCoreCoder flag in GASpecificConfig. #320

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Accept M4A files with invalid dependsOnCoreCoder flag in GASpecificConfig. #320

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23 changes: 18 additions & 5 deletions mp4parse/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3697,7 +3697,7 @@ fn find_descriptor(data: &[u8], esds: &mut ES_Descriptor) -> Result<()> {
read_dc_descriptor(descriptor, esds)?;
}
DECODER_SPECIFIC_TAG => {
read_ds_descriptor(descriptor, esds)?;
read_ds_descriptor(descriptor, esds, ParseStrictness::Permissive)?;
}
_ => {
debug!("Unsupported descriptor, tag {}", tag);
Expand All @@ -3723,7 +3723,11 @@ fn get_audio_object_type(bit_reader: &mut BitReader) -> Result<u16> {
}

/// See MPEG-4 Systems (ISO 14496-1:2010) § 7.2.6.7 and probably 14496-3 somewhere?
fn read_ds_descriptor(data: &[u8], esds: &mut ES_Descriptor) -> Result<()> {
fn read_ds_descriptor(
data: &[u8],
esds: &mut ES_Descriptor,
strictness: ParseStrictness,
) -> Result<()> {
#[cfg(feature = "mp4v")]
// Check if we are in a Visual esda Box.
if esds.video_codec != CodecType::Unknown {
Expand Down Expand Up @@ -3823,9 +3827,18 @@ fn read_ds_descriptor(data: &[u8], esds: &mut ES_Descriptor) -> Result<()> {
};

bit_reader.skip(1)?; // frameLengthFlag
let depend_on_core_order: u8 = ReadInto::read(bit_reader, 1)?;
if depend_on_core_order > 0 {
bit_reader.skip(14)?; // codeCoderDelay
let depends_on_core_coder: u8 = ReadInto::read(bit_reader, 1)?;
if depends_on_core_coder > 0 {
if bit_reader.remaining() < 14 {
fail_if(
strictness != ParseStrictness::Permissive,
"The GASpecificConfig 'coreCoderDelay' field shall be present \
if 'dependsOnCoreCoder' is set per MPEG-4 Audio (ISO 14496-3:2019) § 4.4.1",
)?;
debug!("Insufficient bits for coreCoderDelay, ignoring dependsOnCoreCoder");
} else {
bit_reader.skip(14)?; // coreCoderDelay
}
}
bit_reader.skip(1)?; // extensionFlag

Expand Down
24 changes: 24 additions & 0 deletions mp4parse/src/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1236,6 +1236,30 @@ fn read_esds_invalid_descriptor() {
}
}

#[test]
fn read_esds_depends_on_core_coder_invalid() {
// dependsOnCoreCoder flag is set, but coreCoderDelay bits are not present.
// Extracted from BMO #1709329 audio-stripped.m4a using Bento4.
// "mp4extract --payload-only moov/trak/mdia/minf/stbl/stsd/mp4a/esds audio-stripped.m4a /dev/stdout | xxd -i -c 15"
let esds = vec![
0x03, 0x80, 0x80, 0x80, 0x22, 0x00, 0x01, 0x00, 0x04, 0x80, 0x80, 0x80, 0x14, 0x40, 0x15,
0x00, 0x02, 0x15, 0x00, 0x02, 0x04, 0x88, 0x00, 0x01, 0xea, 0x64, 0x05, 0x80, 0x80, 0x80,
0x02, 0x12, 0x12, 0x06, 0x80, 0x80, 0x80, 0x01, 0x02,
];

let mut stream = make_box(BoxSize::Auto, b"esds", |s| {
s.B32(0) // reserved
.append_bytes(esds.as_slice())
});
let mut iter = super::BoxIter::new(&mut stream);
let mut stream = iter.next_box().unwrap().unwrap();

match super::read_esds(&mut stream) {
Ok(esds) => assert_eq!(esds.audio_codec, super::CodecType::AAC),
_ => panic!("unexpected result with invalid descriptor"),
}
}

#[test]
fn read_esds_redundant_descriptor() {
// the '2' at the end is redundant data.
Expand Down