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Merged
merged 2 commits into from
Oct 21, 2016
Merged

Parse codec specific descriptor to retrieve audio sample rate #39

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948d209
Parse codec specific descriptor to retrieve audio sample rate
Oct 20, 2016
305cc92
Fixed review comments
Oct 21, 2016
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80 changes: 60 additions & 20 deletions mp4parse/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -208,6 +208,7 @@ pub enum SampleEntry {
#[derive(Debug, Clone)]
pub struct ES_Descriptor {
pub audio_codec: CodecType,
pub audio_sample_rate: Option<u32>,
pub codec_specific_config: Vec<u8>,
}

Expand Down Expand Up @@ -1116,8 +1117,15 @@ fn read_flac_metadata<T: Read>(src: &mut BMFFBox<T>) -> Result<FLACMetadataBlock

fn read_esds<T: Read>(src: &mut BMFFBox<T>) -> Result<ES_Descriptor> {
// Tags for elementary stream description
const ESDESCR_TAG: u8 = 0x03;
const DECODER_CONFIG_TAG: u8 = 0x04;
const ESDESCR_TAG: u8 = 0x03;
const DECODER_CONFIG_TAG: u8 = 0x04;
const DECODER_SPECIFIC_TAG: u8 = 0x05;

let frequency_table =
vec![(0x1, 96000), (0x1, 88200), (0x2, 64000), (0x3, 48000),
(0x4, 44100), (0x5, 32000), (0x6, 24000), (0x7, 22050),
(0x8, 16000), (0x9, 12000), (0xa, 11025), (0xb, 8000),
(0xc, 7350)];

let (_, _) = try!(read_fullbox_extra(src));

Expand All @@ -1128,24 +1136,29 @@ fn read_esds<T: Read>(src: &mut BMFFBox<T>) -> Result<ES_Descriptor> {
let esds_array = try!(read_buf(src, esds_size as usize));

// Parsing DecoderConfig descriptor to get the object_profile_indicator
// for correct codec type.
let object_profile_indicator = {
// for correct codec type and audio sample rate.
let (object_profile_indicator, sample_frequency) = {
let mut object_profile: u8 = 0;
let mut sample_frequency = None;

// clone a esds cursor for parsing.
let esds = &mut Cursor::new(&esds_array);
let esds_tag = try!(esds.read_u8());
let next_tag = try!(esds.read_u8());

if esds_tag != ESDESCR_TAG {
if next_tag != ESDESCR_TAG {
return Err(Error::Unsupported("fail to parse ES descriptor"));
}

let esds_extend = try!(esds.read_u8());
// extension tag start from 0x80.
if esds_extend >= 0x80 {
// skip remaining extension and length.
try!(skip(esds, 5));
} else {
let esds_end = if esds_extend >= 0x80 {
// skip remaining extension.
try!(skip(esds, 2));
}
esds.position() + try!(esds.read_u8()) as u64
} else {
esds.position() + esds_extend as u64
};
try!(skip(esds, 2));

let esds_flags = try!(esds.read_u8());

Expand All @@ -1163,19 +1176,45 @@ fn read_esds<T: Read>(src: &mut BMFFBox<T>) -> Result<ES_Descriptor> {
}

// find DecoderConfig descriptor (tag = DECODER_CONFIG_TAG)
let dcds = try!(esds.read_u8());
if dcds != DECODER_CONFIG_TAG {
return Err(Error::Unsupported("fail to parse decoder config descriptor"));
if esds_end > esds.position() {
let next_tag = try!(esds.read_u8());
if next_tag == DECODER_CONFIG_TAG {
let dcds_extend = try!(esds.read_u8());
// extension tag start from 0x80.
if dcds_extend >= 0x80 {
// skip remains extension and length.
try!(skip(esds, 3));
}

object_profile = try!(esds.read_u8());

// Skip uninteresting fields.
try!(skip(esds, 12));
}
}

let dcds_extend = try!(esds.read_u8());
// extension tag start from 0x80.
if dcds_extend >= 0x80 {
// skip remains extension and length.
try!(skip(esds, 3));

// find DecoderSpecific descriptor (tag = DECODER_SPECIFIC_TAG)
if esds_end > esds.position() {
let next_tag = try!(esds.read_u8());
if next_tag == DECODER_SPECIFIC_TAG {
let dsds_extend = try!(esds.read_u8());
// extension tag start from 0x80.
if dsds_extend >= 0x80 {
// skip remains extension and length.
try!(skip(esds, 3));
}

let audio_specific_config = try!(be_u16(esds));

let sample_index = (audio_specific_config & 0x07FF) >> 7;

sample_frequency =
frequency_table.iter().find(|item| item.0 == sample_index).map(|x| x.1);
}
}

try!(esds.read_u8())
(object_profile, sample_frequency)
};

let codec = match object_profile_indicator {
Expand All @@ -1190,6 +1229,7 @@ fn read_esds<T: Read>(src: &mut BMFFBox<T>) -> Result<ES_Descriptor> {

Ok(ES_Descriptor {
audio_codec: codec,
audio_sample_rate: sample_frequency,
codec_specific_config: esds_array,
})
}
Expand Down
4 changes: 2 additions & 2 deletions mp4parse/src/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -831,9 +831,9 @@ fn read_qt_wave_atom() {
.append_repeated(0, 2)
.B8(0x00) // flags
.B8(0x04) // decoder config descriptor tag
.B8(0x06) // dcds length
.B8(0x0d) // dcds length
.B8(0x6b) // mp3
.append_repeated(0, 5)
.append_repeated(0, 12)
}).into_inner();
let wave = make_box(BoxSize::Auto, b"wave", |s| {
s.append_bytes(esds.as_slice())
Expand Down
1 change: 1 addition & 0 deletions mp4parse/tests/public.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,7 @@ fn public_api() {
assert_eq!(match a.codec_specific {
mp4::AudioCodecSpecific::ES_Descriptor(esds) => {
assert_eq!(esds.audio_codec, mp4::CodecType::AAC);
assert_eq!(esds.audio_sample_rate.unwrap(), 48000);
"ES"
}
mp4::AudioCodecSpecific::FLACSpecificBox(_) => {
Expand Down
3 changes: 3 additions & 0 deletions mp4parse_capi/src/lib.rs
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Expand Up @@ -444,6 +444,9 @@ pub unsafe extern fn mp4parse_get_track_audio_info(parser: *mut mp4parse_parser,
}
(*info).codec_specific_config.length = v.codec_specific_config.len() as u32;
(*info).codec_specific_config.data = v.codec_specific_config.as_ptr();
if let Some(rate) = v.audio_sample_rate {
(*info).sample_rate = rate;
}
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match is good to show handling of all branches, or when yielding a value for assignment. For something like this if let is shorter, since the _ => {} clause is equivalent to an omitted empty else clause.

// An ESDS value overrides the track sample rate.
if let Some(rate) = v.audio_sample_rate {
    (*info)sample_rate = rate;
}

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Thanks for suggestion. Fixed.

}
AudioCodecSpecific::FLACSpecificBox(_) => {
return MP4PARSE_ERROR_UNSUPPORTED;
Expand Down