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I have been using Hex file viewer to parse few mp4 files and I know they r coded with H264 not MPEG4 . I do not seem to find the NAL header (0x000001 or 0x00000001) except at very far places from the start of the file , like half or almost at the end ? Any ideas?

user37429
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    "MPEG-4 Part 14: MP4 file format" you should use this if you want to parse MP4 file out. In particular, you will see that Annex B start codes are not used. – Roman R. Feb 22 '16 at 18:25
  • Thx Roman , that makes more sense . I have tried to search for the standard but all I could find is 11 pages of part 14 which does not explain the parsing process , unlike the ITU H264 standards. – user37429 Feb 22 '16 at 20:05

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The extra data can be extracted from the avcC box.

The rest is answered by this post. Possible Locations for Sequence/Picture Parameter Set(s) for H.264 Stream

Community
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szatmary
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  • thx szatmary . That helped a lot , but the documentation is still awful to read. – user37429 Feb 24 '16 at 17:22
  • The documentation around this stuff is multi pass. In order to understand it, you first need to understand it. But once you understand it, it is really great detailed reference material. Most of it is already pretty dense, to expand it to the level of introduction + detailed reference would require volumes of material. So a steep learning curve is the price to pay to be concise. The stuff you are reading was intended to be consumed by people who have been working in media formany years – szatmary Feb 24 '16 at 17:47
  • I see what u saying szatmary , but I still insist it could have been written in a better way. I had no problem understanding the H.264 algorithm itself and I never thought the standard file format would be that hard. I could develop JPEG CODEC before and I never faced such difficulties. – user37429 Feb 24 '16 at 19:51