[Libav-user] Unable to decode AVPacket that are retrieved from AVPacketList.

sithruk sana get2jils at gmail.com
Wed May 21 18:00:16 CEST 2014

Dear all,

    I have been implementing the video [ only] player in android using SDL
and ffmpeg.

     I followed the below approach [from dranger tutorial ]

    1)  There is a linked list with each node of type AVPacketList

        AVPacketList *firstNode=NULL, *lastNode=NULL;

    2)  There are two threads:
        ReadPacket  - Reads packet from av_read_frame, and stores in the
linked list.
        FrameDisplay  - Reads packet from Linked list , decodes the same if
complete packet is received.  Pushes specific event to SDL to render the

    3)  Main Function:
        kick starts two threads ReadPacket, FrameDisplay.


  How can i pass to and from queue ? what is the correct way of doing ?

    In ReadPacket thread:

             AVPacket pkt1, *rpacket=&pkt1;

                     if ( av_read_frame(pFormatCtx, rpacket) >= 0) {
                               if (packet.stream_index == videoStream) {

                           // Creating new node to push..

                           AVPacketList *newNode =
                            newNode->pkt = *rpacket;
                            newNode->next = NULL;
                        //  pushing newNode.


    In FrameDisplay Thread:

        1) Reading node from queue
        2) take the packet like:

            AVPacket *pkt;
            *pkt = newNode->pkt;

        3)  Decode Now:

              avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, pkt);
                           if (frameFinished) {
                                   // I AM UNABLE TO REACH HERE...

*It is the right way to copy the AVPacket structure to and from ?*
ie:  While copying     newNode->pkt  = *rpacket;
     While retrieving  AVPacket *pkt  = newNode->pkt ?

*Surprisingly, instead of keeping the AVPacket in the queue, if i directly
decode, i could able to decode successfully.*
Kindly point out what went wrong ?
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