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LFE channel should always be counted for AC-4 A-JOC content on MPEG-4 layer

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ybai001 2024-12-03 13:29:57 +08:00
parent 547a164f42
commit e503535ec2
1 changed files with 10 additions and 2 deletions
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12
libraries/extractor/src/main/java/androidx/media3/extractor/Ac4Util.java
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@ -410,13 +410,21 @@ public final class Ac4Util {
ac4Presentation.hasBackChannels, ac4Presentation.hasBackChannels,
ac4Presentation.topChannelPairs); ac4Presentation.topChannelPairs);
} else { } else {
channelCount = ac4Presentation.numOfUmxObjects; // The ETSI TS 103 190-2 V1.2.1 (2018-02) specification defines the parameter
// n_umx_objects_minus1 in Annex E (E.11.11) to specify the number of fullband objects. While
// the elementary stream specification (section 6.3.2.8.1) provides information about the
// presence of an LFE channel within the set of dynamic objects, this detail is not explicitly
// stated in the ISO Base Media File Format (Annex E). However, current implementation
// practices consistently include the LFE channel when creating an A-JOC substream. As a
// result, it has been decided that when interpreting the ISO Base Media File Format, the LFE
// channel should always be counted as part of the total channel count.
channelCount = ac4Presentation.numOfUmxObjects + 1; // Here "1" stands for LFE channel
// TODO: There is a bug in ETSI TS 103 190-2 V1.2.1 (2018-02), E.11.11 // TODO: There is a bug in ETSI TS 103 190-2 V1.2.1 (2018-02), E.11.11
// For AC-4 level 4 stream, the intention is to set 19 to n_umx_objects_minus1 but it is // For AC-4 level 4 stream, the intention is to set 19 to n_umx_objects_minus1 but it is
// equal to 15 based on current specification. Dolby has filed a bug report to ETSI. // equal to 15 based on current specification. Dolby has filed a bug report to ETSI.
// The following sentence should be deleted after ETSI specification error is fixed. // The following sentence should be deleted after ETSI specification error is fixed.
if (ac4Presentation.level == 4) { if (ac4Presentation.level == 4) {
channelCount = channelCount == 16 ? 21 : channelCount; channelCount = channelCount == 17 ? 21 : channelCount;
} }
} }