[Libav-user] H264 live stream decoding and got_picture_ptr

Tony Glover T.Glover at nottingham.ac.uk
Thu Sep 6 12:30:01 CEST 2012

Hi all,
                I'm streaming H264 video from a number of webcams to other users over the internet. For the most part this works fine. However, occasionally I get a number of frames with the got_picture_ptr of avcodec_decode_video2() set to 0. This results in a slight pause in the received stream of a couple of seconds. It happens fairly regularly but not sufficiently to render the experience unusable. I've noted that there have been a few previous posts regarding what the meaning of having the flag set to 0 actually signifies, but I haven't come across a definitive answer. The documentation states that it signifies the frame couldn't be decompressed, but what actually causes this to happen?

I'm obviously dropping packets as the data is going over a public network and I'm using RTP to stream the data, so that's to be expected. Is it just a case of not receiving all the frames in a given picture and hence the decoder is struggling to decode the complete picture? All things such as timestamps appear to be OK.

I'm using x264 to encode the data and am using intra-refresh to encode, so I don't get reference (IDR) frames as such, but I do get fragmented NAL's.

Can anybody shed some light on this or suggest an approach when the situation occurs?

Many thanks,

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