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View Full Version : Mp4 muxing and Sample to Chunk Box


Xtoforas
20th October 2008, 22:50
From this thread here (http://forum.doom9.org/showthread.php?p=779001&highlight=stsc#post779001) I figured out what the Sample to Chunk box is used for.

However I'm interested in how the entries are determined in particular how samples_per_chunk are determined. From the linked thread it indicates that when multiple tracks are interleaved there should be multiple entries in the stsc atom but I don't feel like I totally understand this.

When using YAMB to mux a single h264 source I got the following for the stsc atom which would appear to contradict that you should only have multiple entries for interleaved data.

Entry 1
first_chunk - 0x1
samples_per_chunk - 0xD
sample_description_index - 0x1

Entry 2
first_chunk - 0x2
samples_per_chunk - 0xC
sample_description_index - 0x1

Entry 3
first_chunk - 0x214
samples_per_chunk - 0x8
sample_description_index - 0x1

I feel that if I knew how samples_per_chunk was being calculated from the source video I would feel more comfortable with the stream.

Thanks in advance