NAL start code prefix in Sony AVCHD

[orbitlee]

I'm looking at some AVCHD samples, and really confused by the start code prefix.

Here is the hex dump of AVCHD copied from camcoder directly.

Offset 0 1 2 3 4 5 6 7 8 9 A B C D E F

00000300 01 3F 98 C0 47 50 11 10 00 00 01 E0 00 00 85 C0
00000310 0A 31 00 07 13 81 11 00 05 BF 21 00 00 00 01 09
00000320 10 00 00 00 01 27 4D 00 28 F6 02 D0 22 7E FF F0
00000330 00 40 00 31 00 00 12 C0 00 03 A9 80 E8 60 00 F4
00000340 24 00 01 12 A8 AE F2 E3 43 00 07 A1 20 00 08 95
00000350 45 77 97 0E 58 44 22 8B 00 00 00 01 28 EA 43 C8
00000360 00 00 00 01 06 00 0D 80 28 C8 00 87 00 00 28 C8
00000370 00 87 00 40 80 00 00 00 01 06 05 65 17 EE 8C 60
00000380 F8 4D 11 D9 8C D6 08 00 20 0C 9A 66 4D 44 50 4D



Here is the hex dump of AVCHD which is outputed by sony's bundle software(trim on timeline).

Offset 0 1 2 3 4 5 6 7 8 9 A B C D E F

00000300 00 29 56 20 47 50 11 10 00 00 01 E0 00 00 84 C0
00000310 0A 31 00 05 BF 21 11 00 05 A3 01 00 00 00 01 09
00000320 10 00 00 00 01 27 4D 00 28 F6 02 D0 22 7E FF F0
00000330 00 40 00 31 00 00 12 C0 00 03 A9 80 E8 60 00 F4
00000340 24 00 01 12 A8 AE F2 E3 43 00 07 A1 20 00 08 95
00000350 45 77 97 0E 58 44 22 8B 00 00 00 01 28 EA 43 C8
00000360 00 00 01 06 00 0D 80 AF C8 00 00 03 00 00 AF C8
00000370 00 00 03 00 40 80 00 00 01 06 05 65 17 EE 8C 60
00000380 F8 4D 11 D9 8C D6 08 00 20 0C 9A 66 4D 44 50 4D


Did you notice that the difference of NAL at offset 0360 and 0376? The start code prefix is shortened. Can anybody tell me whether this is standard-compliant? Thx!

[crypto]

I haven't gone into detail. That are just some buffer changes. SEI Nals aren't even necessary. So, yes, the stream is still compliant.

[orbitlee]

I raise this question since I try to modify Gabest opensource mpeg splitter to support AVCHD m2ts. Thanks for the information in this thread http://forum.doom9.org/showthread.php?t=111072&page=3&highlight=AVCHD, I can make the AC3 in m2ts be recognizied(unusual PESid). But no video for the second sample. Finally I found open source mpeg splitter insists 00 00 00 01 as start code prefix, so it thinks the second sample(00 00 01) is illegal.
Even if I force it to support 00 00 01 , after connect to CoreAVC, still no video at all.

BTW, I found all NALs(SEIs, slices) afterwards in second samples, use 00 00 01 as start code prefix. and in first samples, 00 00 00 01.