Handle channel count parsing for AC-4 with discrete objects #2526
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Merge latest androidx/media main branch
rohitjoins
reviewed
Jun 24, 2025
| // prevent exceptions, "Maximum number of tracks if audio presentation includes object | ||
| // audio" in table 77 of ETSI TS 103 190-2 V1.2.1 (2018-02) is used as the channel count. | ||
| switch (ac4Presentation.level) { | ||
| case 0: |
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Should this case be part of the default handling in the switch case?
| case 3: | ||
| channelCount = 10; | ||
| break; | ||
| case 4: |
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Table 77 in spec ETSI TS 103 190-2 V1.2.1 (2018-02) states the value 4-6 is reserved, where do we get the value 12 for this?
| case 4: | ||
| channelCount = 12; | ||
| break; | ||
| default: |
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Shouldn't we throw an error from here instead of defaulting to channel count 2?
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Some AC-4 stream consists of sub stream with discrete objects. Due to limitations in the current AC-4 specification (ETSI TS 103 190-2 V1.2.1 (2018-02)), discrete object number information is not explicitly stated in the ISO Base Media File Format (Annex E). To prevent exception triggering, "Maximum number of tracks if audio presentation includes object audio" in table 77 of ETSI TS 103 190-2 V1.2.1 (2018-02) is used as the channel count.
This pull request provides the corresponding implementation in AC4 parser.