/* For reverse playback we use a technique that can be used for
* any keyframe based video codec.
*
* Input:
* Buffer decoding order: 7 8 9 4 5 6 1 2 3 EOS
* Keyframe flag: K K
* Discont flag: D D D
*
* - Each Discont marks a discont in the decoding order.
* - The keyframes mark where we can start decoding.
*
* First we prepend incomming buffers to the gather queue, whenever we receive
* a discont, we flush out the gather queue.
*
* The above data will be accumulated in the gather queue like this:
*
* gather queue: 9 8 7
* D
*
* Whe buffer 4 is received (with a DISCONT), we flush the gather queue like
* this:
*
* while (gather)
* take head of queue and prepend to decode queue.
* if we copied a keyframe, decode the decode queue.
*
* After we flushed the gather queue, we add 4 to the (now empty) gather queue.
* We get the following situation:
*
* gather queue: 4
* decode queue: 7 8 9
*
* After we received 5 (Keyframe) and 6:
*
* gather queue: 6 5 4
* decode queue: 7 8 9
*
* When we receive 1 (DISCONT) which triggers a flush of the gather queue:
*
* Copy head of the gather queue (6) to decode queue:
*
* gather queue: 5 4
* decode queue: 6 7 8 9
*
* Copy head of the gather queue (5) to decode queue. This is a keyframe so we
* can start decoding.
*
* gather queue: 4
* decode queue: 5 6 7 8 9
*
* Decode frames in decode queue, store raw decoded data in output queue, we
* can take the head of the decode queue and prepend the decoded result in the
* output queue:
*
* gather queue: 4
* decode queue:
* output queue: 9 8 7 6 5
*
* Now output all the frames in the output queue, picking a frame from the
* head of the queue.
*
* Copy head of the gather queue (4) to decode queue, we flushed the gather
* queue and can now store input buffer in the gather queue:
*
* gather queue: 1
* decode queue: 4
*
* When we receive EOS, the queue looks like:
*
* gather queue: 3 2 1
* decode queue: 4
*
* Fill decode queue, first keyframe we copy is 2:
*
* gather queue: 1
* decode queue: 2 3 4
*
* Decoded output:
*
* gather queue: 1
* decode queue:
* output queue: 4 3 2
*
* Leftover buffer 1 cannot be decoded and must be discarded.
*/
static GstFlowReturn
theora_dec_flush_decode (GstTheoraDec * dec)
{
GstFlowReturn res = GST_FLOW_OK;
while (dec->decode) {
GstBuffer *buf = GST_BUFFER_CAST (dec->decode->data);
GST_DEBUG_OBJECT (dec, "decoding buffer %p, ts %" GST_TIME_FORMAT,
buf, GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buf)));
/* decode buffer, prepend to output queue */
res = theora_dec_decode_buffer (dec, buf);
/* don't need it anymore now */
gst_buffer_unref (buf);
dec->decode = g_list_delete_link (dec->decode, dec->decode);
}
while (dec->queued) {
GstBuffer *buf = GST_BUFFER_CAST (dec->queued->data);
/* iterate ouput queue an push downstream */
res = gst_pad_push (dec->srcpad, buf);
dec->queued = g_list_delete_link (dec->queued, dec->queued);
}
return res;
}
static GstFlowReturn
theora_dec_chain_forward (GstTheoraDec * dec, gboolean discont,
GstBuffer * buffer)
{
GstFlowReturn result;
result = theora_dec_decode_buffer (dec, buffer);
gst_buffer_unref (buffer);
return result;
}
static GstFlowReturn
theora_dec_handle_frame (GstVideoDecoder * bdec, GstVideoCodecFrame * frame)
{
GstTheoraDec *dec;
GstFlowReturn res;
dec = GST_THEORA_DEC (bdec);
res = theora_dec_decode_buffer (dec, frame->input_buffer, frame);
switch (res) {
case GST_FLOW_OK:
res = gst_video_decoder_finish_frame (bdec, frame);
break;
case GST_CUSTOM_FLOW_DROP:
res = gst_video_decoder_drop_frame (bdec, frame);
break;
default:
gst_video_codec_frame_unref (frame);
break;
}
return res;
}
static gboolean
theora_dec_set_format (GstVideoDecoder * bdec, GstVideoCodecState * state)
{
GstTheoraDec *dec;
dec = GST_THEORA_DEC (bdec);
/* Keep a copy of the input state */
if (dec->input_state)
gst_video_codec_state_unref (dec->input_state);
dec->input_state = gst_video_codec_state_ref (state);
/* FIXME : Interesting, we always accept any kind of caps ? */
if (state->codec_data) {
GstBuffer *buffer;
GstMapInfo minfo;
guint8 *data;
guint size;
guint offset;
buffer = state->codec_data;
gst_buffer_map (buffer, &minfo, GST_MAP_READ);
offset = 0;
size = minfo.size;
data = (guint8 *) minfo.data;
while (size > 2) {
guint psize;
GstBuffer *buf;
psize = (data[0] << 8) | data[1];
/* skip header */
data += 2;
size -= 2;
offset += 2;
/* make sure we don't read too much */
psize = MIN (psize, size);
buf = gst_buffer_copy_region (buffer, GST_BUFFER_COPY_ALL, offset, psize);
/* first buffer is a discont buffer */
if (offset == 2)
GST_BUFFER_FLAG_SET (buf, GST_BUFFER_FLAG_DISCONT);
/* now feed it to the decoder we can ignore the error */
theora_dec_decode_buffer (dec, buf, NULL);
gst_buffer_unref (buf);
/* skip the data */
size -= psize;
data += psize;
offset += psize;
}
gst_buffer_unmap (buffer, &minfo);
}
GST_DEBUG_OBJECT (dec, "Done");
return TRUE;
}
