[Mp4-tech] Header format for slicing, data partitioning in byte stream format

[ashfiqua tahseen]

Hi Mr. Winter,
 Thanks for your reply.
 Actually, I am trying to identify only the NALUs; not their type. I used the start code prefix (SCP) 000001 to search each NALU. But when I use slicing or data partitioning, the SCP format (000001) comes per frame basis. But it should come per packet where a data partition or a slice is encapsulated in a packet. So I am confused how to get the starting of a NALU.
I'll highly appreciate any suggestion in this regard.
Thanking you,
Ashfiqua Tahseen Connie
Tom Winter <tommytrue gmail.com> wrote: hello,
Looks like some of the thing that you are trying to do are ones similar to one I am trying to do ,but  I am not trying to drop packets but trying to insert some bit errors in NAL.
Well to your question
you are confusing me between SCP(start code prefix) with NAL header.
 Each NAL start is indicated by SCP then NAL header follows. So if you want to identify the NAL type u should read NAL headers 4th bit after SCP, so basically u discard SCP then read header, but SCP are necessary to identify NAL start and end, this is the way u identify the packets,
 Some notes if u are using RTP mode its is very easy to identify between packets since it gives NAL type and its length's in header and SCP is not necessary, wheres in Annex B u need to read whole stream and calculate lenght and type by parsing for SCP.
 Looks like we can share some info here since we are trying to do similar work.
Regards
Tom
On Feb 13, 2024 4:41 PM, ashfiqua tahseen <ashfiqua03 yahoo.com> wrote:
 Hi,
  I am using JM13.1 as my codec. I want to drop some packet from the encoded file. For example, suppose, I have en cncoded file foreman.264 and a loss pattern where I have 1 for correctly received packet and 0 for lost packet. I want to read the foreman.264 file, compare it with the loss pattern and then write it to another file, say, test.264.
   I am using byte stream format; and try to do some tests using data partitioning and slicing. I assumed that since each slice or data partition will be encapsulated in a single NALU, the header should always be 00000001. But I have figured out that, this format (00000001) comes on per frame. I want to know what should the header format be if I use slicing or data partitioning or none of them in byte stream format. I mean what the criterion on basis of which I can separate the packets.
  Any suggestion will be highly appreciated.
  Thanking you,
  Ashfiqua Tahseen Connie
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Tom Winter ,
Graduate Student ,
UNC Charlotte 
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