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d0b757886e
ExoPlayer assumed 4-bytes for length in two places (by assuming the
length is the same as the 4-byte NAL start code):
1. In `AvcConfig` we transform length-delimited to start-delimited
before writing into `initializationData`, and then skip
'nal unit length field' bytes when parsing from `initializationData`
(when we should skip 'start code length' bytes instead).
2. In `Mp4Extractor.readSample` we modify the local variable
`sampleSize` to fix the difference between length field length and
start code length, but **only on the first attempt to read a
sample**. If we are resuming in the middle of reading a sample (after
a recoverable I/O error), this fix for `sampleSize` is not done,
which means we end up missing the last 2-3 bytes of the sample when
the NAL length is 1-2 bytes.
* This is fixed by moving the `sampleSize` 'fixing' code to outside
the `if (sampleCurrentNalBytesRemaining == 0)` block.
* `FragmentedMp4Extractor` has very similar code, but uses a
field for `sampleSize`, rather than a local, so doesn't look
vulnerable to the same problem (though I haven't totally
tested this).
This change adds a test file with 2-byte NAL lengths, generated by
hacking the media3 muxer to emit 2-byte NAL lengths and transforming
`sample.mp4` using the transformer demo app.
PiperOrigin-RevId: 713709203