解码帧

给定编解码器上下文和来自媒体流的编码数据包，你可以开始将媒体解码为原始帧。要解码单个帧，可以使用以下代码：

// A codec context, and some encoded data packet from a stream/file, given.
AVCodecContext *codecContext;  // See Open a codec context
AVPacket *packet;              // See the Reading Media topic

// Send the data packet to the decoder
int sendPacketResult = avcodec_send_packet(codecContext, packet);
if (sendPacketResult == AVERROR(EAGAIN)){
    // Decoder can't take packets right now. Make sure you are draining it.
}else if (sendPacketResult < 0){
    // Failed to send the packet to the decoder
}

// Get decoded frame from decoder
AVFrame *frame = av_frame_alloc();
int decodeFrame = avcodec_receive_frame(codecContext, frame);

if (decodeFrame == AVERROR(EAGAIN)){
    // The decoder doesn't have enough data to produce a frame
    // Not an error unless we reached the end of the stream
    // Just pass more packets until it has enough to produce a frame
    av_frame_unref(frame);
    av_freep(frame);
}else if (decodeFrame < 0){
    // Failed to get a frame from the decoder
    av_frame_unref(frame);
    av_freep(frame);
}

// Use the frame (ie. display it)

如果要解码所有帧，可以简单地将前面的代码放在一个循环中，然后连续输入数据包。