Merge pull request #138 from ebarnard/alac

Support alac (Apple lossless audio codec)

Author: rillian

mp4parse/src/boxes.rs

@@ -138,4 +138,5 @@ box_database!(
     MP3AudioSampleEntry               0x2e6d7033, // ".mp3" - from F4V.
     CompositionOffsetBox              0x63747473, // "ctts"
     LPCMAudioSampleEntry              0x6C70636D, // "lpcm" - quicktime atom
+    ALACSpecificBox                   0x616C6163, // "alac" - Also used by ALACSampleEntry
 );

mp4parse/src/lib.rs

@@ -316,6 +316,7 @@ pub enum AudioCodecSpecific {
     ES_Descriptor(ES_Descriptor),
     FLACSpecificBox(FLACSpecificBox),
     OpusSpecificBox(OpusSpecificBox),
+    ALACSpecificBox(ALACSpecificBox),
     MP3,
     LPCM,
 }
@@ -392,6 +393,13 @@ pub struct OpusSpecificBox {
     channel_mapping_table: Option<ChannelMappingTable>,
 }
 
+/// Represent an ALACSpecificBox 'alac'
+#[derive(Debug, Clone)]
+pub struct ALACSpecificBox {
+    version: u8,
+    pub data: Vec<u8>,
+}
+
 #[derive(Debug)]
 pub struct MovieExtendsBox {
     pub fragment_duration: Option<MediaScaledTime>,
@@ -464,6 +472,7 @@ pub enum CodecType {
     EncryptedVideo,
     EncryptedAudio,
     LPCM,   // QT
+    ALAC,
 }
 
 impl Default for CodecType {
@@ -1689,6 +1698,28 @@ pub fn serialize_opus_header<W: byteorder::WriteBytesExt + std::io::Write>(opus:
     Ok(())
 }
 
+/// Parse `ALACSpecificBox`.
+fn read_alac<T: Read>(src: &mut BMFFBox<T>) -> Result<ALACSpecificBox> {
+    let (version, flags) = read_fullbox_extra(src)?;
+    if version != 0 {
+        return Err(Error::Unsupported("unknown alac (ALAC) version"));
+    }
+    if flags != 0 {
+        return Err(Error::InvalidData("no-zero alac (ALAC) flags"));
+    }
+
+    let length = src.bytes_left();
+    if length != 24 && length != 48 {
+        return Err(Error::InvalidData("ALACSpecificBox magic cookie is the wrong size"));
+    }
+    let data = read_buf(src, length)?;
+
+    Ok(ALACSpecificBox {
+        version: version,
+        data: data,
+    })
+}
+
 /// Parse a hdlr box.
 fn read_hdlr<T: Read>(src: &mut BMFFBox<T>) -> Result<HandlerBox> {
     let (_, _) = read_fullbox_extra(src)?;
@@ -1900,6 +1931,15 @@ fn read_audio_sample_entry<T: Read>(src: &mut BMFFBox<T>) -> Result<(CodecType,
                 codec_type = CodecType::Opus;
                 codec_specific = Some(AudioCodecSpecific::OpusSpecificBox(dops));
             }
+            BoxType::ALACSpecificBox => {
+                if name != BoxType::ALACSpecificBox ||
+                    codec_specific.is_some() {
+                    return Err(Error::InvalidData("malformed audio sample entry"));
+                }
+                let alac = read_alac(&mut b)?;
+                codec_type = CodecType::ALAC;
+                codec_specific = Some(AudioCodecSpecific::ALACSpecificBox(alac));
+            }
             BoxType::QTWaveAtom => {
                 let qt_esds = read_qt_wave_atom(&mut b)?;
                 codec_type = qt_esds.audio_codec;

mp4parse/src/tests.rs

@@ -653,6 +653,28 @@ fn serialize_opus_header() {
     ]);
 }
 
+#[test]
+fn read_alac() {
+    let mut stream = make_box(BoxSize::Auto, b"alac", |s| {
+        s.append_repeated(0, 6) // reserved
+         .B16(1) // data reference index
+         .B32(0) // reserved
+         .B32(0) // reserved
+         .B16(2) // channel count
+         .B16(16) // bits per sample
+         .B16(0) // pre_defined
+         .B16(0) // reserved
+         .B32(44100 << 16) // Sample rate
+         .append_bytes(&make_fullbox(BoxSize::Auto, b"alac", 0, |s| {
+             s.append_bytes(&vec![0xfa; 24])
+         }).into_inner())
+    });
+    let mut iter = super::BoxIter::new(&mut stream);
+    let mut stream = iter.next_box().unwrap().unwrap();
+    let r = super::read_audio_sample_entry(&mut stream);
+    assert!(r.is_ok());
+}
+
 #[test]
 fn avcc_limit() {
     let mut stream = make_box(BoxSize::Auto, b"avc1", |s| {

mp4parse/tests/public.rs

@@ -96,6 +96,10 @@ fn public_api() {
                         assert!(opus.version > 0);
                         "Opus"
                     }
+                    mp4::AudioCodecSpecific::ALACSpecificBox(alac) => {
+                        assert!(alac.data.len() == 24 || alac.data.len() == 48);
+                        "ALAC"
+                    }
                     mp4::AudioCodecSpecific::MP3 => {
                         "MP3"
                     }

mp4parse_capi/src/lib.rs

@@ -98,6 +98,7 @@ pub enum Mp4parseCodec {
     Jpeg,   // for QT JPEG atom in video track
     Ac3,
     Ec3,
+    Alac,
 }
 
 impl Default for Mp4parseCodec {
@@ -429,6 +430,8 @@ pub unsafe extern fn mp4parse_get_track_info(parser: *mut Mp4parseParser, track_
                 Mp4parseCodec::Unknown,
             AudioCodecSpecific::MP3 =>
                 Mp4parseCodec::Mp3,
+            AudioCodecSpecific::ALACSpecificBox(_) =>
+                Mp4parseCodec::Alac,
         },
         Some(SampleEntry::Video(ref video)) => match video.codec_specific {
             VideoCodecSpecific::VPxConfig(_) =>
@@ -565,6 +568,10 @@ pub unsafe extern fn mp4parse_get_track_audio_info(parser: *mut Mp4parseParser,
                 }
             }
         }
+        AudioCodecSpecific::ALACSpecificBox(ref alac) => {
+            (*info).extra_data.length = alac.data.len() as u32;
+            (*info).extra_data.data = alac.data.as_ptr();
+        }
         AudioCodecSpecific::MP3 | AudioCodecSpecific::LPCM => (),
     }