Parse ESDS. #38
Parse ESDS. #38
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Structure of ESDS:
ESDS box
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|- ES descriptor
|- 3 bytes extension (optional)
|- 1 byte length
|- 2 bytes ES ID
|- 1 byte stream priority and flags
|- stream dependency (optional, depends on flags)
| |- 2 bytes
|- url (optional, depends on flags)
| |- 1 byte length
| |- x bytes, x is the length
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|- Decoder Config descriptior
|- 3 bytes extension (optional)
|- 1 byte length
|- 1 byte object profile indicator
We need to get object profile indicator for the codec type.
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We also want to get the "real" sample rate out of the ESDS to fix issue #30, but that can be done separately to this PR. |
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Ok, I'll address issue #30 later. Do we also need to parse ESDS in VideoSampleEntry? |
Probably not at this stage. libstagefright only parses it to extract accurate audio metadata; for video it's just exporting the entire ESDS as a binary blob without inspecting it. |
| let esds_array = try!(read_buf(src, esds_size as usize)); | ||
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| // clone a esds cursor for parsing. | ||
| let esds = &mut Cursor::new(esds_array.clone()); |
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Rather than cloning the data, share it by creating the Cursor with a ref. You just need to arrange for the Cursor to goe out of scope before you try to move esds_array into EsDescriptor.
| @@ -1398,7 +1471,8 @@ fn read_audio_sample_entry<T: Read>(src: &mut BMFFBox<T>, track: &mut Track) -> | |||
| } | |||
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| let esds = try!(read_esds(&mut b)); | |||
| codec_specific = Some(esds); | |||
| track.codec_type = esds.audio_codec; | |||
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For consistency, set track.codec_type and codec_specific in the same order in each of the branches - right now there's a mix of both variants.
| @@ -23,6 +24,10 @@ mod tests; | |||
| // Arbitrary buffer size limit used for raw read_bufs on a box. | |||
| const BUF_SIZE_LIMIT: u64 = 1024 * 1024; | |||
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| // Tags for elementary stream description | |||
| const ESDESCR_TAG: u8 = 0x03; | |||
| const DECODER_CONFIG_TAG: u8 = 0x04; | |||
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These are only used inside read_esds, so move them into the scope of the function.
| #[allow(non_camel_case_types)] | ||
| #[derive(Debug, Clone)] | ||
| pub enum AudioCodecSpecific { | ||
| ES_Descriptor(Vec<u8>), | ||
| EsDescriptor(EsDescriptor), |
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Keep the name ES_Descriptor to match the spec reference.
| let esds_extend = try!(esds.read_u8()); | ||
| // extension tag start from 0x80. | ||
| if esds_extend >= 0x80 { | ||
| // skip remains extension and length. |
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| let esds_flags = try!(esds.read_u8()); | ||
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| // Stream dependnecy flag, first bit from left most. |
| // Url flag, second bit from left most. | ||
| if esds_flags & 0x40 > 0 { | ||
| // Skip uninteresting fields. | ||
| let skip_es_len = try!(esds.read_u8()) + 2; |
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It'd be safer to make skip_es_len a usize and cast the result of the read before adding to avoid potential overflows.
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Great, thanks! |
Structure of ESDS:
ESDS box
|
|- ES descriptor
| |- 3 bytes extension (optional)
| |- 1 byte length
| |- 2 bytes ES ID
| |- 1 byte stream priority and flags
| |- stream dependency (optional, depends on flags)
| | |- 2 bytes
| |- url (optional, depends on flags)
| | |- 1 byte length
| | |- x bytes, x is the length
| |
| |- Decoder Config descriptior
| |- 3 bytes extension (optional)
| |- 1 byte length
| |- 1 byte object profile indicator
We need to get object profile indicator for the codec type.