Format of AC3 in PES?

[unixfs]

Hi,
can someone explain what's the format of AC3 in 0xBD PES packets, please?
Especially,
- what's the meaning of the 3 bytes before 0x8n track id?
- is there any limitation I should consider regarding the size of
the PES packet?

Thanks.

[mpucoder]

Are you sure you mean the three bytes before the substream number? Those are part of the PES header (specifically the last byte of PTS and the P-STD buffer size)
The three bytes following the substream number contain the number of audio frame headers (1 byte) and the first access unit pointer (2 bytes). You can see these using VobEdit.
The first access unit pointer is a biased byte offset to the audio frame header corresponding to the Pack PTS. The value 0000 indicates there is no access unit corresponding to PTS, 0001 points to the header immediately following the pointer.
All Packs in DVD are 2048 bytes long, every PES must fit exactly into the remaining bytes of the Pack (length will always be 0x07ec until the data for the VOBU is exhausted, and then a shorter packet may be used followed by a filler packet). The data itself is merely broken up to fit the space (packetized) without regard to content.

[unixfs]

right, after 0x8n, not before.
Thanks for your explanation!