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mpeg2: rework generation of presentation timestamps.

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Always prefer PTS from the demuxer layer for GOP times. If this is invalid,
i.e. demuxer could not determine the PTS or the generated PTS is lower than
max PTS from past pictures, then try to fix it up based on the duration of
a frame.

For picture PTS, simply use the GOP PTS formerly computed then use TSN to
reconstruct a current time. Also now handle wrapped TSN correctly.
This commit is contained in:
Gwenole Beauchesne 2012-03-30 16:23:33 +02:00
parent 6eeb20a953
commit d51bb87482
1 changed files with 105 additions and 22 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

127
gst-libs/gst/vaapi/gstvaapidecoder_mpeg2.c
View file

@ -61,6 +61,102 @@ G_DEFINE_TYPE(GstVaapiDecoderMpeg2,
} \
} G_STMT_END
/* PTS Generator */
typedef struct _PTSGenerator PTSGenerator;
struct _PTSGenerator {
GstClockTime gop_pts; // Current GOP PTS
GstClockTime max_pts; // Max picture PTS
guint gop_tsn; // Absolute GOP TSN
guint max_tsn; // Max picture TSN, relative to last GOP TSN
guint ovl_tsn; // How many times TSN overflowed since GOP
guint lst_tsn; // Last picture TSN
guint fps_n;
guint fps_d;
};
static void
pts_init(PTSGenerator *tsg)
{
tsg->gop_pts = GST_CLOCK_TIME_NONE;
tsg->max_pts = GST_CLOCK_TIME_NONE;
tsg->gop_tsn = 0;
tsg->max_tsn = 0;
tsg->ovl_tsn = 0;
tsg->lst_tsn = 0;
tsg->fps_n = 0;
tsg->fps_d = 0;
}
static inline GstClockTime
pts_get_duration(PTSGenerator *tsg, guint num_frames)
{
return gst_util_uint64_scale(num_frames,
GST_SECOND * tsg->fps_d, tsg->fps_n);
}
static void
pts_set_framerate(PTSGenerator *tsg, guint fps_n, guint fps_d)
{
tsg->fps_n = fps_n;
tsg->fps_d = fps_d;
}
static void
pts_sync(PTSGenerator *tsg, GstClockTime gop_pts)
{
guint gop_tsn;
if (!GST_CLOCK_TIME_IS_VALID(gop_pts) ||
(GST_CLOCK_TIME_IS_VALID(tsg->max_pts) && tsg->max_pts >= gop_pts)) {
/* Invalid GOP PTS, interpolate from the last known picture PTS */
if (GST_CLOCK_TIME_IS_VALID(tsg->max_pts)) {
gop_pts = tsg->max_pts + pts_get_duration(tsg, 1);
gop_tsn = tsg->gop_tsn + tsg->ovl_tsn * 1024 + tsg->max_tsn + 1;
}
else {
gop_pts = 0;
gop_tsn = 0;
}
}
else {
/* Interpolate GOP TSN from this valid PTS */
if (GST_CLOCK_TIME_IS_VALID(tsg->gop_pts))
gop_tsn = tsg->gop_tsn + gst_util_uint64_scale(
gop_pts - tsg->gop_pts, tsg->fps_n, GST_SECOND * tsg->fps_d);
else
gop_tsn = 0;
}
tsg->gop_pts = gop_pts;
tsg->gop_tsn = gop_tsn;
tsg->max_tsn = 0;
tsg->ovl_tsn = 0;
tsg->lst_tsn = 0;
}
static GstClockTime
pts_eval(PTSGenerator *tsg, GstClockTime pic_pts, guint pic_tsn)
{
GstClockTime pts;
if (!GST_CLOCK_TIME_IS_VALID(tsg->gop_pts))
tsg->gop_pts = 0;
pts = tsg->gop_pts + pts_get_duration(tsg, tsg->ovl_tsn * 1024 + pic_tsn);
if (!GST_CLOCK_TIME_IS_VALID(tsg->max_pts) || tsg->max_pts < pts)
tsg->max_pts = pts;
if (tsg->max_tsn < pic_tsn)
tsg->max_tsn = pic_tsn;
else if (tsg->max_tsn == 1023 && pic_tsn < tsg->lst_tsn) { /* TSN wrapped */
tsg->max_tsn = pic_tsn;
tsg->ovl_tsn++;
}
tsg->lst_tsn = pic_tsn;
return pts;
}
struct _GstVaapiDecoderMpeg2Private {
GstVaapiProfile profile;
guint width;
@ -75,9 +171,7 @@ struct _GstVaapiDecoderMpeg2Private {
GstVaapiPicture *current_picture;
GstVaapiDpb *dpb;
GstAdapter *adapter;
GstClockTime seq_pts;
GstClockTime gop_pts;
GstClockTime pts_diff;
PTSGenerator tsg;
guint is_constructed : 1;
guint is_opened : 1;
guint has_seq_ext : 1;
@ -204,6 +298,8 @@ gst_vaapi_decoder_mpeg2_open(GstVaapiDecoderMpeg2 *decoder, GstBuffer *buffer)
priv->dpb = gst_vaapi_dpb_mpeg2_new();
if (!priv->dpb)
return FALSE;
pts_init(&priv->tsg);
return TRUE;
}
@ -363,10 +459,9 @@ decode_sequence(GstVaapiDecoderMpeg2 *decoder, guchar *buf, guint buf_size)
priv->fps_n = seq_hdr->fps_n;
priv->fps_d = seq_hdr->fps_d;
pts_set_framerate(&priv->tsg, priv->fps_n, priv->fps_d);
gst_vaapi_decoder_set_framerate(base_decoder, priv->fps_n, priv->fps_d);
priv->seq_pts = gst_adapter_prev_timestamp(priv->adapter, NULL);
priv->width = seq_hdr->width;
priv->height = seq_hdr->height;
priv->has_seq_ext = FALSE;
@ -400,6 +495,7 @@ decode_sequence_ext(GstVaapiDecoderMpeg2 *decoder, guchar *buf, guint buf_size)
if (seq_ext->fps_n_ext && seq_ext->fps_d_ext) {
priv->fps_n *= seq_ext->fps_n_ext + 1;
priv->fps_d *= seq_ext->fps_d_ext + 1;
pts_set_framerate(&priv->tsg, priv->fps_n, priv->fps_d);
gst_vaapi_decoder_set_framerate(base_decoder, priv->fps_n, priv->fps_d);
}
@ -477,17 +573,8 @@ decode_gop(GstVaapiDecoderMpeg2 *decoder, guchar *buf, guint buf_size)
gop.hour, gop.minute, gop.second, gop.frame,
priv->closed_gop, priv->broken_link);
pts = GST_SECOND * (gop.hour * 3600 + gop.minute * 60 + gop.second);
pts += gst_util_uint64_scale(gop.frame, GST_SECOND * priv->fps_d, priv->fps_n);
if (priv->gop_pts != GST_CLOCK_TIME_NONE && pts <= priv->gop_pts) {
/* Try to fix GOP timestamps, based on demux timestamps */
pts = gst_adapter_prev_timestamp(priv->adapter, NULL);
if (pts != GST_CLOCK_TIME_NONE)
pts -= priv->pts_diff;
}
priv->gop_pts = pts;
if (!priv->pts_diff)
priv->pts_diff = priv->seq_pts - priv->gop_pts;
pts = gst_adapter_prev_timestamp(priv->adapter, NULL);
pts_sync(&priv->tsg, pts);
return GST_VAAPI_DECODER_STATUS_SUCCESS;
}
@ -558,9 +645,8 @@ decode_picture(GstVaapiDecoderMpeg2 *decoder, guchar *buf, guint buf_size)
}
/* Update presentation time */
pts = priv->gop_pts;
pts += gst_util_uint64_scale(pic_hdr->tsn, GST_SECOND * priv->fps_d, priv->fps_n);
picture->pts = pts + priv->pts_diff;
pts = gst_adapter_prev_timestamp(priv->adapter, NULL);
picture->pts = pts_eval(&priv->tsg, pts, pic_hdr->tsn);
return status;
}
@ -957,9 +1043,6 @@ gst_vaapi_decoder_mpeg2_init(GstVaapiDecoderMpeg2 *decoder)
priv->profile = GST_VAAPI_PROFILE_MPEG2_SIMPLE;
priv->current_picture = NULL;
priv->adapter = NULL;
priv->seq_pts = GST_CLOCK_TIME_NONE;
priv->gop_pts = GST_CLOCK_TIME_NONE;
priv->pts_diff = 0;
priv->is_constructed = FALSE;
priv->is_opened = FALSE;
priv->has_seq_ext = FALSE;