video: change VideoDecoder::decode() prototype

This patch fixes frame buffer usage outside of this function
by moving packet buffer creation into the caller.
The caller is now responsible for creating and destroying it.

This fix crashes found during shm_sink rendering.

Note: only reproducible with libav _prior_ to commit 759001c534287a96dc96d1e274665feb7059145d:

    Author:    Anton Khirnov <anton at khirnov.net>
    Committer: Anton Khirnov <anton at khirnov.net>
    Date:      Wed Nov 21 21:34:46 2012 +0100

    lavc decoders: work with refcounted frames.

Refs #49174

Change-Id: I3900a64690568a1ecf107ccfc07a2952981eefa4

daemon/src/video/video_decoder.cpp

@@ -194,10 +194,8 @@ int VideoDecoder::setupFromVideoData()
 }
 
 VideoDecoder::Status
-VideoDecoder::decode(VideoFrame& result)
+VideoDecoder::decode(VideoFrame& result, VideoPacket& video_packet)
 {
-    // Guarantee that we free the packet every iteration
-    VideoPacket video_packet;
     AVPacket *inpacket = video_packet.get();
     int ret = av_read_frame(inputCtx_, inpacket);
     if (ret == AVERROR(EAGAIN)) {

daemon/src/video/video_decoder.h

@@ -65,7 +65,7 @@ namespace sfl_video {
         int openInput(const std::string &source_str,
                       const std::string &format_str);
         int setupFromVideoData();
-        Status decode(VideoFrame&);
+        Status decode(VideoFrame&, VideoPacket&);
         Status flush(VideoFrame&);
 
         int getWidth() const;

daemon/src/video/video_input.cpp

@@ -110,8 +110,8 @@ int VideoInput::interruptCb(void *data)
 
 bool VideoInput::captureFrame()
 {
-    VideoFrame& frame = getNewFrame();
-    const auto ret = decoder_->decode(frame);
+    VideoPacket pkt;
+    const auto ret = decoder_->decode(getNewFrame(), pkt);
 
     switch (ret) {
         case VideoDecoder::Status::FrameFinished:

daemon/src/video/video_receive_thread.cpp

@@ -185,7 +185,8 @@ void VideoReceiveThread::addIOContext(SocketPair &socketPair)
 
 bool VideoReceiveThread::decodeFrame()
 {
-    const auto ret = videoDecoder_->decode(getNewFrame());
+    VideoPacket pkt;
+    const auto ret = videoDecoder_->decode(getNewFrame(), pkt);
 
     switch (ret) {
         case VideoDecoder::Status::FrameFinished: