I have video shot using a Sony PXW-Z280V using AVC_3840_2160_HP@L51 with 29.97 frame rate. Upon analyzing the MXF file structure, I notice that the Index Entry Array seems incorrect. In particular the KeyFrameOffset values for the first two B-frames in every GOP points back two prior I-frames.

See the following entries (especially #16, #17). To me it looks like the frame offset values for these two frames should be -1, -2 instead of -16, -17. Is this a problem with the Sony codec implementation, or something I'm not understanding correctly?

# TempOffs KeyOffs Flags StreamOffs Sl.Offs# 0
0 1 0 0xC4 R S . . . 1 I 0x000000000000 2357760
1 1 -1 0x13 . . . Bp. . B 0x000000244E00 162816
2 -2 -2 0x13 . . . Bp. . B 0x000000271E00 278528
3 1 -3 0x22 . . Fp. . . P 0x0000002BB200 488448
4 1 -4 0x33 . . FpBp. . B 0x000000337A00 211456
5 -2 -5 0x33 . . FpBp. . B 0x000000370800 297472
6 1 -6 0x22 . . Fp. . . P 0x0000003BE600 553984
7 1 -7 0x33 . . FpBp. . B 0x00000044AE00 315392
8 -2 -8 0x33 . . FpBp. . B 0x00000049D200 293888
9 1 -9 0x22 . . Fp. . . P 0x0000004EA200 612864
10 1 -10 0x33 . . FpBp. . B 0x000000585000 305152
11 -2 -11 0x33 . . FpBp. . B 0x0000005D4C00 306688
12 1 -12 0x22 . . Fp. . . P 0x000000624E00 585216
13 1 -13 0x33 . . FpBp. . B 0x0000006B9000 316928
14 -2 -14 0x33 . . FpBp. . B 0x00000070BA00 299008
15 1 0 0x40 . S . . . . I 0x000000759E00 582656
16 1 -16 0x33 . . FpBp. . B 0x0000007ED600 302080
17 -2 -17 0x33 . . FpBp. . B 0x00000083C600 236032
18 1 -3 0x22 . . Fp. . . P 0x00000087B400 650240
19 1 -4 0x33 . . FpBp. . B 0x00000091F400 246784
20 -2 -5 0x33 . . FpBp. . B 0x000000960C00 252416
21 1 -6 0x22 . . Fp. . . P 0x0000009A3A00 649216
22 1 -7 0x33 . . FpBp. . B 0x000000A47600 251904
23 -2 -8 0x33 . . FpBp. . B 0x000000A8A200 249856
24 1 -9 0x22 . . Fp. . . P 0x000000ACC600 649216
25 1 -10 0x33 . . FpBp. . B 0x000000B70200 252928
26 -2 -11 0x33 . . FpBp. . B 0x000000BB3200 250368
27 1 -12 0x22 . . Fp. . . P 0x000000BF5800 643584
28 1 -13 0x33 . . FpBp. . B 0x000000C97E00 249856
29 -2 -14 0x33 . . FpBp. . B 0x000000CDA200 247808
30 1 0 0x40 . S . . . . I 0x000000D1BE00 951808
31 1 -16 0x33 . . FpBp. . B 0x000000E09800 246272
32 -2 -17 0x33 . . FpBp. . B 0x000000E4AE00 235520
33 1 -3 0x22 . . Fp. . . P 0x000000E89A00 663552
34 1 -4 0x33 . . FpBp. . B 0x000000F30E00 239104