check channelcounts in CSD (#40)

* check channelcounts in CSD
* Fix channel count in test

Author: alfredoyang

mp4parse/src/lib.rs

@@ -209,6 +209,7 @@ pub enum SampleEntry {
 pub struct ES_Descriptor {
     pub audio_codec: CodecType,
     pub audio_sample_rate: Option<u32>,
+    pub audio_channel_count: Option<u16>,
     pub codec_specific_config: Vec<u8>,
 }
 
@@ -1136,10 +1137,11 @@ 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 and audio sample rate.
-    let (object_profile_indicator, sample_frequency) = {
+    // for correct codec type, audio sample rate and channel counts.
+    let (object_profile_indicator, sample_frequency, channels) = {
         let mut object_profile: u8 = 0;
         let mut sample_frequency = None;
+        let mut channels = None;
 
         // clone a esds cursor for parsing.
         let esds = &mut Cursor::new(&esds_array);
@@ -1209,12 +1211,16 @@ fn read_esds<T: Read>(src: &mut BMFFBox<T>) -> Result<ES_Descriptor> {
 
                 let sample_index = (audio_specific_config & 0x07FF) >> 7;
 
+                let channel_counts = (audio_specific_config & 0x007F) >> 3;
+
                 sample_frequency =
                     frequency_table.iter().find(|item| item.0 == sample_index).map(|x| x.1);
+
+                channels = Some(channel_counts);
             }
         }
 
-        (object_profile, sample_frequency)
+        (object_profile, sample_frequency, channels)
     };
 
     let codec = match object_profile_indicator {
@@ -1230,6 +1236,7 @@ fn read_esds<T: Read>(src: &mut BMFFBox<T>) -> Result<ES_Descriptor> {
     Ok(ES_Descriptor {
         audio_codec: codec,
         audio_sample_rate: sample_frequency,
+        audio_channel_count: channels,
         codec_specific_config: esds_array,
     })
 }

mp4parse_capi/examples/test.cc

@@ -166,7 +166,7 @@ void test_arg_validation_with_data(const std::string& filename)
   memset(&audio, 0, sizeof(audio));
   rv = mp4parse_get_track_audio_info(parser, 1, &audio);
   assert(rv == MP4PARSE_OK);
-  assert(audio.channels == 2);
+  assert(audio.channels == 1);
   assert(audio.bit_depth == 16);
   assert(audio.sample_rate == 48000);
 

mp4parse_capi/src/lib.rs

@@ -447,6 +447,9 @@ pub unsafe extern fn mp4parse_get_track_audio_info(parser: *mut mp4parse_parser,
             if let Some(rate) = v.audio_sample_rate {
                 (*info).sample_rate = rate;
             }
+            if let Some(channels) = v.audio_channel_count {
+                (*info).channels = channels;
+            }
         }
         AudioCodecSpecific::FLACSpecificBox(ref flac) => {
             // Return the STREAMINFO metadata block in the codec_specific.
@@ -801,7 +804,7 @@ fn arg_validation_with_data() {
 
         let mut audio = Default::default();
         assert_eq!(MP4PARSE_OK, mp4parse_get_track_audio_info(parser, 1, &mut audio));
-        assert_eq!(audio.channels, 2);
+        assert_eq!(audio.channels, 1);
         assert_eq!(audio.bit_depth, 16);
         assert_eq!(audio.sample_rate, 48000);