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-rw-r--r--DOCS/man/options.rst15
-rw-r--r--demux/demux.c103
2 files changed, 80 insertions, 38 deletions
diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index f55b38eb7a..754c2476f8 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -568,6 +568,21 @@ Playback Control
depending on the exact conditions. You may have to use the
``--vd-lavc-show-all`` option as well.
+``--video-backward-batch=<number>``, ``--audio-backward-batch=<number>``
+ Number of keyframe ranges to decode at once when backward decoding (default:
+ 1 for video, 10 for audio). Another pointless tuning parameter nobody should
+ use. This should affect performance only. In theory, setting a number higher
+ than 1 for audio will reduce overhead due to less frequent backstep
+ operations and less redundant decoding work due to fewer decoded overlap
+ frames (see ``--audio-backward-overlap``). On the other hand, it requires
+ a larger reversal buffer, and could make playback less smooth due to
+ breaking pipelining (e.g. by decoding a lot, and then doing nothing for a
+ while).
+
+ It probably never makes sense to set ``--video-backward-batch``. But in
+ theory, it could help with intra-only video codecs by reducing backstep
+ operations.
+
``--demuxer-backward-playback-step=<seconds>``
Number of seconds the demuxer should seek back to get new packets during
backward playback (default: 60). This is useful for tuning backward
diff --git a/demux/demux.c b/demux/demux.c
index 5b830284ec..f732cf9e6c 100644
--- a/demux/demux.c
+++ b/demux/demux.c
@@ -91,6 +91,7 @@ struct demux_opts {
char *record_file;
int video_back_preroll;
int audio_back_preroll;
+ int back_batch[STREAM_TYPE_COUNT];
double back_seek_size;
};
@@ -118,6 +119,8 @@ const struct m_sub_options demux_conf = {
1024, ({"auto", -1})),
OPT_CHOICE_OR_INT("audio-backward-overlap", audio_back_preroll, 0, 0,
1024, ({"auto", -1})),
+ OPT_INTRANGE("video-backward-batch", back_batch[STREAM_VIDEO], 0, 0, 1024),
+ OPT_INTRANGE("audio-backward-batch", back_batch[STREAM_AUDIO], 0, 0, 1024),
OPT_DOUBLE("demuxer-backward-playback-step", back_seek_size, M_OPT_MIN,
.min = 0),
{0}
@@ -134,6 +137,10 @@ const struct m_sub_options demux_conf = {
.video_back_preroll = -1,
.audio_back_preroll = -1,
.back_seek_size = 60,
+ .back_batch = {
+ [STREAM_VIDEO] = 1,
+ [STREAM_AUDIO] = 10,
+ },
},
};
@@ -343,8 +350,8 @@ struct demux_stream {
double last_ret_dts;
// Backwards demuxing.
- // pos/dts of the previous keyframe packet returned; valid if
- // back_range_started or back_restarting are set.
+ // pos/dts of the previous keyframe packet returned; always valid if back-
+ // demuxing is enabled, and back_restart_eof/back_restart_next are false.
int64_t back_restart_pos;
double back_restart_dts;
bool back_restart_eof; // restart position is at EOF; overrides pos/dts
@@ -360,8 +367,10 @@ struct demux_stream {
bool back_resuming; // resuming mode (above fields are valid/used)
// Set to true if the first packet (keyframe) of a range was returned.
bool back_range_started;
- // Number of packets at start of range yet to return. -1 is used for BOF.
- int back_range_min;
+ // Number of KF packets at start of range yet to return. -1 is used for BOF.
+ int back_range_count;
+ // Number of KF packets yet to return that are marked as preroll.
+ int back_range_preroll;
// Static packet preroll count.
int back_preroll;
@@ -752,7 +761,8 @@ static void ds_clear_reader_state(struct demux_stream *ds,
ds->back_resume_dts = MP_NOPTS_VALUE;
ds->back_resuming = false;
ds->back_range_started = false;
- ds->back_range_min = 0;
+ ds->back_range_count = 0;
+ ds->back_range_preroll = 0;
}
}
@@ -1350,43 +1360,43 @@ static void find_backward_restart_pos(struct demux_stream *ds)
}
// Find where to restart demuxing. It's usually the last keyframe packet
- // before restart_pos, but might be up to back_preroll packets earlier.
-
- struct demux_packet *last_keyframe = NULL; // keyframe before back_restart
+ // before restart_pos, but might be up to back_preroll + batch keyframe
+ // packets earlier.
// (Normally, we'd just iterate backwards, but no back links.)
int num_kf = 0;
- struct demux_packet *pre_1 = NULL; // idiotic "optimization" for preroll=1
+ struct demux_packet *pre_1 = NULL; // idiotic "optimization" for total=1
for (struct demux_packet *dp = first; dp != back_restart; dp = dp->next) {
if (dp->keyframe) {
num_kf++;
- pre_1 = last_keyframe; // 1 keyframe before final last_keyframe
- last_keyframe = dp;
+ pre_1 = dp;
}
}
+ // Number of renderable keyframes to return to user.
+ // (Excludes preroll, which is decoded by user, but then discarded.)
+ int batch = MPMAX(in->opts->back_batch[ds->type], 1);
+ // Number of keyframes to return to the user in total.
+ int total = batch + ds->back_preroll;
+
+ assert(total >= 1);
+
struct demux_packet *target = NULL; // resume pos
- int got_preroll = 0; // nr. of keyframes, incl. target, excl. last_keyframe
+ // nr. of keyframes, incl. target, excl. restart_pos
+ int got_total = num_kf < total && ds->queue->is_bof ? num_kf : total;
+ int got_preroll = MPMAX(got_total - batch, 0);
- if (ds->back_preroll == 0) {
- target = last_keyframe;
- } else if (ds->back_preroll == 1) {
+ if (got_total == 1) {
target = pre_1;
- if (!target && ds->queue->is_bof)
- target = last_keyframe;
- got_preroll = target == pre_1 ? 1 : 0;
- } else if (num_kf > ds->back_preroll || ds->queue->is_bof) {
- got_preroll = ds->back_preroll;
- if (num_kf <= ds->back_preroll && ds->queue->is_bof)
- got_preroll = MPMAX(0, num_kf - 1);
+ } else if (got_total <= num_kf) {
int cur_kf = 0;
for (struct demux_packet *dp = first; dp != back_restart; dp = dp->next) {
if (dp->keyframe) {
- cur_kf++;
- if (num_kf - cur_kf == got_preroll) {
+ if (num_kf - cur_kf == got_total) {
target = dp;
break;
}
+ cur_kf++;
}
}
}
@@ -1399,7 +1409,8 @@ static void find_backward_restart_pos(struct demux_stream *ds)
MP_VERBOSE(in, "BOF for stream %d\n", ds->index);
ds->back_restarting = false;
ds->back_range_started = false;
- ds->back_range_min = -1;
+ ds->back_range_count = -1;
+ ds->back_range_preroll = 0;
ds->need_wakeup = true;
wakeup_ds(ds);
return;
@@ -1423,9 +1434,26 @@ static void find_backward_restart_pos(struct demux_stream *ds)
if (seek_pts != MP_NOPTS_VALUE)
ds->back_seek_pos = seek_pts;
+ // For next backward adjust action.
+ struct demux_packet *restart_pkt = NULL;
+ int kf_pos = 0;
+ for (struct demux_packet *dp = target; dp; dp = dp->next) {
+ if (dp->keyframe) {
+ if (kf_pos == got_preroll) {
+ restart_pkt = dp;
+ break;
+ }
+ kf_pos++;
+ }
+ }
+ assert(restart_pkt);
+ ds->back_restart_dts = restart_pkt->dts;
+ ds->back_restart_pos = restart_pkt->pos;
+
ds->back_restarting = false;
ds->back_range_started = false;
- ds->back_range_min = got_preroll + 1;
+ ds->back_range_count = got_total;
+ ds->back_range_preroll = got_preroll;
ds->need_wakeup = true;
wakeup_ds(ds);
return;
@@ -2263,7 +2291,7 @@ static int dequeue_packet(struct demux_stream *ds, struct demux_packet **res)
return -1;
// Next keyframe (or EOF) was reached => step back.
- if (ds->back_range_started && !ds->back_range_min &&
+ if (ds->back_range_started && !ds->back_range_count &&
((ds->reader_head && ds->reader_head->keyframe) || eof))
{
ds->back_restarting = true;
@@ -2276,7 +2304,7 @@ static int dequeue_packet(struct demux_stream *ds, struct demux_packet **res)
return 0;
}
- eof = ds->back_range_min < 0;
+ eof = ds->back_range_count < 0;
}
ds->need_wakeup = !ds->reader_head;
@@ -2301,21 +2329,20 @@ static int dequeue_packet(struct demux_stream *ds, struct demux_packet **res)
pkt->next = NULL;
if (in->back_demuxing) {
- if (ds->back_range_min && pkt->keyframe)
- ds->back_range_min -= 1;
- if (ds->back_range_min) {
- pkt->back_preroll = true;
- } else if (pkt->keyframe) {
- // For next backward adjust action.
- ds->back_restart_dts = pkt->dts;
- ds->back_restart_pos = pkt->pos;
- ds->back_restart_eof = false;
+ if (pkt->keyframe) {
+ assert(ds->back_range_count > 0);
+ ds->back_range_count -= 1;
+ if (ds->back_range_preroll >= 0)
+ ds->back_range_preroll -= 1;
}
+
+ if (ds->back_range_preroll >= 0)
+ pkt->back_preroll = true;
+
if (!ds->back_range_started) {
pkt->back_restart = true;
ds->back_range_started = true;
}
- ds->back_seek_pos = MP_PTS_MIN(ds->back_seek_pos, pkt->pts);
}
double ts = MP_PTS_OR_DEF(pkt->dts, pkt->pts);
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-04 14:03:33 +0000