I need to be able to inspect ts packets (looking at video PID 481) and determine whether the packet contains an IDR frame. My understanding is that I need to look for a NAL unit start code, and then something else after that to signify it's the start of an IDR frame. Please can someone clarify?
Here's an example of a packet that I think is an IDR frame, but need to be able to prove it from the payload data:
* Packet 2
---- TS Header ----
PID: 481 (0x01E1), header size: 12, sync: 0x47
Error: 0, unit start: 1, priority: 0
Scrambling: 0, continuity counter: 1
Adaptation field: yes (8 bytes), payload: yes (176 bytes)
Discontinuity: 1, random access: 1, ES priority: 0
PCR: 0x000000013A5
---- PES Header ----
Stream id: 0xE0 (Video 0)
PES packet length: 0 (unbounded)
---- Full TS Packet Content ----
47 41 E1 31 07 D0 00 00 00 08 7E E5 00 00 01 E0 00 00 84 C0 0A 31 00 05
E5 CD 11 00 05 AD 8D 00 00 00 01 09 10 00 00 00 01 67 64 00 29 AC D9 40
78 04 4F DE 02 94 04 04 05 00 00 03 00 01 00 00 03 00 32 E6 80 00 F4 24
00 04 F5 8A 49 30 0F 8B 16 CB 00 00 00 01 68 FA A7 CB 00 00 01 06 00 05
95 6C 60 E4 85 80 00 00 01 06 05 FF FF F5 DC 45 E9 BD E6 D9 48 B7 96 2C
D8 20 D9 23 EE EF 78 32 36 34 20 2D 20 63 6F 72 65 20 31 34 38 20 2D 20
48 2E 32 36 34 2F 4D 50 45 47 2D 34 20 41 56 43 20 63 6F 64 65 63 20 2D
20 43 6F 70 79 72 69 67 68 74 20 32 30 30 33 2D 32 30 31 36
Its not possible to tell from that packet. It is however VERY likely it is an IDR. I say its likely, because looking at the NALUs, I can see an AUD 00 00 00 01 09, an SPS 00 00 00 01 67 a PPS 00 00 00 01 68 then an SEI 00 00 01 06
The SEI however takes the remaining bytes of the packet, You will need to continue reading packets from that PID until you fine the next NALU and see if its an IDR.