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videodecoder: refactor and document finish_frame some more

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* Move the in-flight iteration and handling code into the main block
* Document the intent a bit more

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4694>
This commit is contained in:
Edward Hervey 2023-05-07 09:27:16 +02:00 committed by GStreamer Marge Bot
parent bce9f3327d
commit 386a8dbae5
1 changed files with 82 additions and 77 deletions
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55
subprojects/gst-plugins-base/gst-libs/gst/video/gstvideodecoder.c
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@ -2976,7 +2976,9 @@ gst_video_decoder_prepare_finish_frame (GstVideoDecoder *
{
GstVideoDecoderPrivate *priv = decoder->priv;
GList *l, *events = NULL;
gboolean sync;
gboolean sync, frames_without_dts, frames_without_pts;
GstClockTime min_dts, min_pts;
GstVideoCodecFrame *earliest_dts_frame, *earliest_pts_frame;
#ifndef GST_DISABLE_GST_DEBUG
GST_LOG_OBJECT (decoder, "n %d in %" G_GSIZE_FORMAT " out %" G_GSIZE_FORMAT,
@ -3046,15 +3048,20 @@ gst_video_decoder_prepare_finish_frame (GstVideoDecoder *
GST_TIME_ARGS (frame->duration));
}
/* PTS is expected monotone ascending,
* so a good guess is lowest unsent DTS */
{
GstClockTime min_dts = GST_CLOCK_TIME_NONE;
GstClockTime min_pts = GST_CLOCK_TIME_NONE;
GstVideoCodecFrame *earliest_dts_frame = NULL;
GstVideoCodecFrame *earliest_pts_frame = NULL;
gboolean frames_without_dts = FALSE;
gboolean frames_without_pts = FALSE;
/* The following code is to fix issues with PTS and DTS:
* * Because the input PTS and/or DTS was mis-used (using DTS as PTS, or PTS
* as DTS)
* * Because the input was missing PTS and/or DTS
*
* For that, we will collected 3 important information from the frames in
* flight:
* * Whether all frames had a valid PTS or a valid DTS
* * Which frame has the lowest PTS (and its value)
* * Which frame has the lowest DTS (And its value)
*/
frames_without_pts = frames_without_dts = FALSE;
min_dts = min_pts = GST_CLOCK_TIME_NONE;
earliest_pts_frame = earliest_dts_frame = NULL;
/* Check what is the earliest PTS and DTS in our pendings frames */
for (l = priv->frames.head; l; l = l->next) {
@ -3087,10 +3094,14 @@ gst_video_decoder_prepare_finish_frame (GstVideoDecoder *
earliest_pts_frame->abidata.ABI.ts2 = frame->abidata.ABI.ts2;
}
/* and set if needed;
* valid delta means we have reasonable DTS input */
/* also, if we ended up reordered, means this approach is conflicting
* with some sparse existing PTS, and so it does not work out */
/* First attempt at recovering missing PTS:
* * If we figured out the PTS<->DTS delta (from a keyframe)
* * AND all frames have a valid DTS (i.e. it is not sparsely timestamped
* input)
* * AND we are not dealing with ordering issues
*
* We can figure out the pts from the lowest DTS and the PTS<->DTS delta
*/
if (!priv->reordered_output &&
!GST_CLOCK_TIME_IS_VALID (frame->pts) && !frames_without_dts &&
GST_CLOCK_TIME_IS_VALID (priv->pts_delta)) {
@ -3100,10 +3111,8 @@ gst_video_decoder_prepare_finish_frame (GstVideoDecoder *
GST_TIME_ARGS (frame->pts));
}
}
/* if we detected reordered output, then PTS are void,
* however those were obtained; bogus input, subclass etc */
/* if we detected reordered output, then PTS are void, however those were
* obtained; bogus input, subclass etc */
if (priv->reordered_output && !frames_without_pts) {
GST_DEBUG_OBJECT (decoder, "invalidating PTS");
frame->pts = GST_CLOCK_TIME_NONE;
@ -3117,8 +3126,6 @@ gst_video_decoder_prepare_finish_frame (GstVideoDecoder *
"no valid PTS, using oldest PTS %" GST_TIME_FORMAT,
GST_TIME_ARGS (frame->pts));
}
}
if (frame->pts == GST_CLOCK_TIME_NONE) {
/* Last ditch timestamp guess: Just add the duration to the previous
@ -3145,17 +3152,15 @@ gst_video_decoder_prepare_finish_frame (GstVideoDecoder *
}
}
if (GST_CLOCK_TIME_IS_VALID (priv->last_timestamp_out)) {
if (frame->pts < priv->last_timestamp_out) {
if (GST_CLOCK_TIME_IS_VALID (priv->last_timestamp_out) &&
frame->pts < priv->last_timestamp_out) {
GST_WARNING_OBJECT (decoder,
"decreasing timestamp (%" GST_TIME_FORMAT " < %"
GST_TIME_FORMAT ")",
"decreasing timestamp (%" GST_TIME_FORMAT " < %" GST_TIME_FORMAT ")",
GST_TIME_ARGS (frame->pts), GST_TIME_ARGS (priv->last_timestamp_out));
priv->reordered_output = TRUE;
/* make it a bit less weird downstream */
frame->pts = priv->last_timestamp_out;
}
}
if (GST_CLOCK_TIME_IS_VALID (frame->pts))
priv->last_timestamp_out = frame->pts;