How to find SPS and PPS string in H264 codec from mp4

Question

As you all know that in Smooth Stream client manifest file, contains a "CodecPrivateData" attribute in video tag. Now after my initial investigation I found that this string is formed by using SPS and PPS which are essentially NAL units.

I am looking for a way to extract that information from video GOP, so that I can use the same to create manifest file and manually substitute codec private data

Basically, i am looking forward to create custom app to create smooth representation using ffmpeg

Just to clarify, so you want to use ffmpeg to extract SPS and PPS from an .mp4 container programatically or this is a one time extraction of SPS/PPS from a single .mp4 file? — Aki, Jul 10 '13 at 08:08
well to be honest ffmpeg is just an option, I would be ok if any other tool is also available which can help me in getting SPS/PPS from mp4.Regarding your question, not sure if i understand it correctly. But I am ok with anyway, I just need to extract SPS and PPS from mp4 — Tarun, Jul 10 '13 at 09:37

Aki · Answer 1 · 2013-07-19T08:52:57.293

Note that SPS/PPS are stored separately from video track in the mp4 file in one of the global headers(avcC portion of the global header).

Here is format: 8+ bytes per ISO/IEC 14496-10

                 = long unsigned offset + long ASCII text string 'avcC'
                -> 1 byte version = 8-bit hex version  (current = 1)
                -> 1 byte H.264 profile = 8-bit unsigned stream profile
                -> 1 byte H.264 compatible profiles = 8-bit hex flags
                -> 1 byte H.264 level = 8-bit unsigned stream level
                -> 1 1/2 nibble reserved = 6-bit unsigned value set to 63
                -> 1/2 nibble NAL length = 2-bit length byte size type
                  - 1 byte = 0 ; 2 bytes = 1 ; 4 bytes = 3
                -> 1 byte number of SPS = 8-bit unsigned total
                -> 2+ bytes SPS length = short unsigned length
                -> + SPS NAL unit = hexdump
                -> 1 byte number of PPS = 8-bit unsigned total
                -> 2+ bytes PPS length = short unsigned length
                -> + PPS NAL unit = hexdump

If you just want to extract SPS/PPS from a single .mp4, you can use hex editor and get the SPS/PPS by inspection based on the MP4 format specs above(look for "avcC" string by searching from the end of the file); and then add the SPS/PPS bytes to an c-style array for your use.

Otherwise you can use ffmpeg together with h264bitstream utility to extract SPS/PPS. First run ffmpeg on the command line to extract h264 stream:

ffmpeg -i my_funny_video.mp4 -vcodec copy -vbsf h264_mp4toannexb -an my_funny_video.h264

Then run h264_analyze from the h264bitstream utility:

h264_analyze my_funny_video.h264

which will product a detailed analysis on your SPS/PPS and other NALs.

I am not sure how can I use ffmpeg to extract SPS/PPS? It will be huge favour if you can guide on that too? — Tarun, Jul 11 '13 at 08:39
Also I am able to trace the SPS and PPS using C#, But after analyizing I found that PPS / SPS string length can vary depending on video. Do they follow any pattern — Tarun, Jul 12 '13 at 06:47

How to find SPS and PPS string in H264 codec from mp4

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