gst_element_add_pad (GST_ELEMENT (dec), dec->srcpad);
dec->crop = THEORA_DEF_CROP;
+ dec->gather = NULL;
+ dec->decode = NULL;
dec->queued = NULL;
}
if (format != GST_FORMAT_TIME)
goto newseg_wrong_format;
- if (rate <= 0.0)
- goto newseg_wrong_rate;
-
/* now configure the values */
gst_segment_set_newsegment_full (&dec->segment, update,
rate, arate, format, start, stop, time);
gst_event_unref (event);
goto done;
}
-newseg_wrong_rate:
- {
- GST_DEBUG_OBJECT (dec, "negative rates not supported yet");
- gst_event_unref (event);
- goto done;
- }
}
static GstFlowReturn
}
static GstFlowReturn
-theora_dec_chain (GstPad * pad, GstBuffer * buf)
+theora_dec_chain_forward (GstTheoraDec * dec, gboolean discont, GstBuffer * buf)
{
- GstTheoraDec *dec;
ogg_packet packet;
GstFlowReturn result = GST_FLOW_OK;
- dec = GST_THEORA_DEC (gst_pad_get_parent (pad));
-
/* resync on DISCONT */
- if (G_UNLIKELY (GST_BUFFER_FLAG_IS_SET (buf, GST_BUFFER_FLAG_DISCONT))) {
+ if (G_UNLIKELY (discont)) {
GST_DEBUG_OBJECT (dec, "received DISCONT buffer");
dec->need_keyframe = TRUE;
dec->last_timestamp = -1;
/* interpolate granule pos */
dec->granulepos = _inc_granulepos (dec, dec->granulepos);
- gst_object_unref (dec);
-
gst_buffer_unref (buf);
return result;
}
+/* 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 an 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);
+
+ /* FIXME, decode buffer, prepend to output queue */
+ 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_reverse (GstTheoraDec * dec, gboolean discont, GstBuffer * buf)
+{
+ GstFlowReturn res = GST_FLOW_OK;
+
+ /* if we have a discont, move buffers to the decode list */
+ if (discont) {
+ while (dec->gather) {
+ GstBuffer *buf;
+ guint8 *data;
+
+ buf = GST_BUFFER_CAST (dec->gather->data);
+ /* remove from the gather list */
+ dec->gather = g_list_delete_link (dec->gather, dec->gather);
+ /* copy to decode queue */
+ dec->decode = g_list_prepend (dec->decode, buf);
+
+ /* if we copied a keyframe, flush and decode the decode queue */
+ data = GST_BUFFER_DATA (buf);
+ if ((data[0] & 0x40) == 0)
+ res = theora_dec_flush_decode (dec);
+ }
+ }
+
+ /* add buffer to gather queue */
+ dec->gather = g_list_prepend (dec->gather, buf);
+
+ return res;
+}
+
+static GstFlowReturn
+theora_dec_chain (GstPad * pad, GstBuffer * buf)
+{
+ GstTheoraDec *dec;
+ GstFlowReturn res;
+ gboolean discont;
+
+ dec = GST_THEORA_DEC (gst_pad_get_parent (pad));
+
+ /* peel of DISCONT flag */
+ discont = GST_BUFFER_FLAG_IS_SET (buf, GST_BUFFER_FLAG_DISCONT);
+
+ if (dec->segment.rate > 0.0)
+ res = theora_dec_chain_forward (dec, discont, buf);
+ else
+ res = theora_dec_chain_reverse (dec, discont, buf);
+
+ gst_object_unref (dec);
+
+ return res;
+}
+
static GstStateChangeReturn
theora_dec_change_state (GstElement * element, GstStateChange transition)
{
projects / platform / upstream / gst-plugins-base.git / commitdiff