Thank you for your answers and suggestions. Regards, Miladin
From: live-devel [mailto:[email protected]] On Behalf Of Joshua Kordani Sent: 20 June 2014 15:05 To: [email protected] Subject: Re: [Live-devel] Decoding H264 non-IDR picture On 6/20/14 5:42 AM, Miladin Sajic wrote: Hi, I am trying to implement decoding of H264 NAL units that are received from the camera (using live555 rtsp streaming). Everything works fine if received NAL unit is IDR (see part of the code in PS) but it does not work for SLICE NAL unit (nal_unit_type == 1). To decode image this NAL unit is not enough on its own and reference needs to be made to all the units since last IDR unit (key frame with nal_unit_type == 5). I do not know how to implement this. How to combine last IDR unit with the following SLICE NAL units to produce H264 frame before sending it to the decoder? [cid:[email protected]] Can you give me any advice or point me to the right direction? Any help is greatly appreciated. _______________________________________________ live-devel mailing list [email protected]<mailto:[email protected]> http://lists.live555.com/mailman/listinfo/live-devel Sorry Ross for continuing the OT discussion, but just real quick. The answer to your decoding question lies in the question itself, you said that non idr slices can reference any prior nal up to the last idr. So in order to decode, you need to pass all prior nals up to the last idr. How exactly you do this depends on the decoder library you're using, ie ffmpeg requires that you provide the full bitstream each call to the decoder, hence (sc = startcode) sps sc pps sc idr frame 1 sps sc pps sc idr sc slice frame 2 sps sc pps sc idr sc slice sc slice frame 3 and so on. I can imagine a decoding library frontend that keeps track of the unchanging parts of the bitstream for you, and I wonder why it doesn't already exist, ie you pass nals in receive order to the decoder library and then ask the library to give you a frame. Eventually, once it has enough info, you get a frame back each call, while only having to briefly store the latest nal on behalf of the library. I know this is OT, but if I'm mistaken someone please speak up. -- Joshua Kordani LSA Autonomy
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