I'm a software tester and I need to test a certain requirement for a vehicle camera that I'm not sure on how to test. As in the title it's to verify that each frame is encoded with a single slice. This is done for more efficient encoding.

AVTP/h264, configured with high profile, to have only I-frames, progressively encoded.

I'm not that knowledgeable with imaging and video streaming, so any help would be appreciated.

1 Answer 1


You can use ffmpeg (and grep) to do this.


ffmpeg -i H264file -c copy -bsf:v trace_headers -f null - 2>&1 | grep first_mb_in_slice

This should print out lines of the form

[trace_headers @ 000002087b24c3c0] 8   first_mb_in_slice                     1 = 0
[trace_headers @ 000002087b24c3c0] 8   first_mb_in_slice     00000000101000001 = 320
[trace_headers @ 000002087b24c3c0] 8   first_mb_in_slice   0000000001010000001 = 640

If each frame is a single slice then ALL lines will have value 0 (1 = 0) for first_mb_in_slice. A non-zero value indicates sliced encoding.

  • Thank you. This is helpful and does workout.
    – Bivas
    Commented Apr 13, 2022 at 6:11

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