Per ISO 14496-1 § 7.2.6.7.2, the semantics of decoder specific inform…

…ation

depend on the value of DecoderConfigDescriptor.objectTypeIndication. But for
audio, mp4parse treats all decoder specific information as if it has the bit
syntax defined for object type indication 0x40. This is not the case for
object type indications 0x69 and 0x6B, which now have more recently defined
decoder specific information with a distinct bit syntax, which Mozilla code
can disregard. This allows tracks carrying MP3 audio to be parsed correctly
when the new decoder specific info is present.

mp4parse/src/lib.rs

@@ -379,6 +379,7 @@ pub enum SampleEntry {
 #[allow(non_camel_case_types)]
 #[derive(Debug, Default)]
 pub struct ES_Descriptor {
+    pub object_profile: u8,
     pub audio_codec: CodecType,
     pub audio_object_type: Option<u16>,
     pub extended_audio_object_type: Option<u16>,
@@ -2452,7 +2453,16 @@ fn find_descriptor(data: &[u8], esds: &mut ES_Descriptor) -> Result<()> {
                 read_dc_descriptor(descriptor, esds)?;
             }
             DECODER_SPECIFIC_TAG => {
-                read_ds_descriptor(descriptor, esds)?;
+                match esds.object_profile {
+                    0x69 | 0x6B => {
+                        // Could parse these object types' decoder specific info
+                        // to discover the MPEG audio layer, etc., if needed.
+                        break;
+                    }
+                    _ => {
+                        read_ds_descriptor(descriptor, esds)?;
+                    }
+                };
             }
             _ => {
                 debug!("Unsupported descriptor, tag {}", tag);
@@ -2647,7 +2657,7 @@ fn read_surround_channel_count(bit_reader: &mut BitReader, channels: u8) -> Resu
 /// See ISO 14496-1:2010 § 7.2.6.6
 fn read_dc_descriptor(data: &[u8], esds: &mut ES_Descriptor) -> Result<()> {
     let des = &mut Cursor::new(data);
-    let object_profile = des.read_u8()?;
+    esds.object_profile = des.read_u8()?;
 
     // Skip uninteresting fields.
     skip(des, 12)?;
@@ -2656,9 +2666,9 @@ fn read_dc_descriptor(data: &[u8], esds: &mut ES_Descriptor) -> Result<()> {
         find_descriptor(&data[des.position().try_into()?..data.len()], esds)?;
     }
 
-    esds.audio_codec = match object_profile {
+    esds.audio_codec = match esds.object_profile {
         0x40 | 0x41 => CodecType::AAC,
-        0x6B => CodecType::MP3,
+        0x69 | 0x6B => CodecType::MP3,
         _ => CodecType::Unknown,
     };