Video Stream Start Codes for Different Codecs

Start Code Prefix (SCP)
H.264 and MPEG-4 Stream contain various codes that are identified by a common 3 byte string = 0x 00 00 01

H.264

SCP Identifies beginning of NAL Unit.

Stream Structure:
1. NAL Unit Code - 1 byte
2. NAL Unit Data

Anatomy of 1 byte = 8 bits of NAL Unit Code:
1 Bit - Always zero
2 Bits - 0 for non ref frames. Non zero for SPS, PPS and Ref frame.
5 bits - NAL Unit Type. 1 - Non IDR, 5 - IDR, 7 - SPS, 8 - PPS.

Typical NAL Unit Codes:
x7- SPS
x8 - PPS
x5 - IDR
x1- Reference P
01 - Non ref P
Note: x is non zero

Typical Stream:
00 00 00 01 67(SPS) 42 00 1E AA 40 28 02 DC 80 00 00 00 01 68(PPS) CE 38 80 00 00 00 01 65(IDR) 88 ..... 00 00 01 41(Non IDR Ref) 9A 44 ....

MPEG-4

Stream Struct:

1. Video object start code - 00 through 1F

2. Video object layer start code - 20 through 2F

3. Video Object Layer Info - Length and value depends upon content

3. vop start code - B6

4. VOP Info

Typical MP-4 Bitstream:

00 00 01 00(vo Start) 00 00 01 20(vol start) 00 C8 89 80 0C C9 10 3F 00 00 01 B6(vop start) 10 61 60 ...