[FFmpeg-devel] [PATCH v2 2/7] avformat/imf: add support for input seeking
pal at sandflow.com
pal at sandflow.com
Mon Feb 21 08:02:25 EET 2022
From: Pierre-Anthony Lemieux <pal at palemieux.com>
The IMF demuxer did not implement AVInputFormat::read_seek2(), resulting in
inefficient input seeking.
Addresses https://trac.ffmpeg.org/ticket/9648
Byte- and frame-seeking are not supported.
---
libavformat/imfdec.c | 129 ++++++++++++++++++++++++++++++++++---------
1 file changed, 102 insertions(+), 27 deletions(-)
diff --git a/libavformat/imfdec.c b/libavformat/imfdec.c
index b98af020d2..f208b262c3 100644
--- a/libavformat/imfdec.c
+++ b/libavformat/imfdec.c
@@ -359,13 +359,15 @@ static IMFAssetLocator *find_asset_map_locator(IMFAssetLocatorMap *asset_map, FF
}
static int open_track_resource_context(AVFormatContext *s,
- IMFVirtualTrackResourcePlaybackCtx *track_resource)
+ IMFVirtualTrackPlaybackCtx *track,
+ int32_t resource_index)
{
IMFContext *c = s->priv_data;
int ret = 0;
- int64_t entry_point;
+ int64_t seek_offset = 0;
AVDictionary *opts = NULL;
AVStream *st;
+ IMFVirtualTrackResourcePlaybackCtx *track_resource = track->resources + resource_index;
if (track_resource->ctx) {
av_log(s,
@@ -416,32 +418,27 @@ static int open_track_resource_context(AVFormatContext *s,
st = track_resource->ctx->streams[0];
- /* Warn if the resource time base does not match the file time base */
- if (av_cmp_q(st->time_base, av_inv_q(track_resource->resource->base.edit_rate)))
- av_log(s,
- AV_LOG_WARNING,
- "Incoherent source stream timebase " AVRATIONAL_FORMAT
- "regarding resource edit rate: " AVRATIONAL_FORMAT,
- st->time_base.num,
- st->time_base.den,
- track_resource->resource->base.edit_rate.den,
- track_resource->resource->base.edit_rate.num);
-
- entry_point = av_rescale_q(track_resource->resource->base.entry_point, st->time_base,
- av_inv_q(track_resource->resource->base.edit_rate));
-
- if (entry_point) {
- av_log(s,
- AV_LOG_DEBUG,
- "Seek at resource %s entry point: %" PRIu32 "\n",
- track_resource->locator->absolute_uri,
- track_resource->resource->base.entry_point);
- ret = avformat_seek_file(track_resource->ctx, 0, entry_point, entry_point, entry_point, 0);
+ /* Determine the seek offset into the Track File, taking into account:
+ * - the current timestamp within the virtual track
+ * - the entry point of the resource
+ */
+ if (imf_time_to_ts(&seek_offset,
+ av_sub_q(track->current_timestamp, track_resource->ts_offset),
+ st->time_base))
+ av_log(s, AV_LOG_WARNING, "Incoherent stream timebase " AVRATIONAL_FORMAT
+ "and composition timeline position: " AVRATIONAL_FORMAT "\n",
+ st->time_base.num, st->time_base.den,
+ track->current_timestamp.den, track->current_timestamp.num);
+
+ if (seek_offset) {
+ av_log(s, AV_LOG_DEBUG, "Seek at resource %s entry point: %" PRIi64 "\n",
+ track_resource->locator->absolute_uri, seek_offset);
+ ret = avformat_seek_file(track_resource->ctx, 0, seek_offset, seek_offset, seek_offset, 0);
if (ret < 0) {
av_log(s,
AV_LOG_ERROR,
"Could not seek at %" PRId64 "on %s: %s\n",
- entry_point,
+ seek_offset,
track_resource->locator->absolute_uri,
av_err2str(ret));
avformat_close_input(&track_resource->ctx);
@@ -584,7 +581,7 @@ static int set_context_streams_from_tracks(AVFormatContext *s)
AVStream *first_resource_stream;
/* Open the first resource of the track to get stream information */
- ret = open_track_resource_context(s, &c->tracks[i]->resources[0]);
+ ret = open_track_resource_context(s, c->tracks[i], 0);
if (ret)
return ret;
first_resource_stream = c->tracks[i]->resources[0].ctx->streams[0];
@@ -774,7 +771,7 @@ static int get_resource_context_for_timestamp(AVFormatContext *s, IMFVirtualTrac
"Switch resource on track %d: re-open context\n",
track->index);
- ret = open_track_resource_context(s, track->resources + i);
+ ret = open_track_resource_context(s, track, i);
if (ret != 0)
return ret;
if (track->current_resource_index > 0)
@@ -942,6 +939,83 @@ static int imf_probe(const AVProbeData *p)
return AVPROBE_SCORE_MAX;
}
+static void rescale_interval(AVRational tb_in, AVRational tb_out,
+ int64_t *min_ts, int64_t *ts, int64_t *max_ts)
+{
+ *ts = av_rescale_q(*ts, tb_in, tb_out);
+ *min_ts = av_rescale_q_rnd(*min_ts, tb_in, tb_out, AV_ROUND_UP | AV_ROUND_PASS_MINMAX);
+ *max_ts = av_rescale_q_rnd(*max_ts, tb_in, tb_out, AV_ROUND_DOWN | AV_ROUND_PASS_MINMAX);
+}
+
+static int coherent_ts(int64_t ts, AVRational in_tb, AVRational out_tb)
+{
+ int dst_num;
+ int dst_den;
+ int ret;
+
+ ret = av_reduce(&dst_num, &dst_den, ts * in_tb.num * out_tb.den,
+ in_tb.den * out_tb.num, INT64_MAX);
+ if (!ret || dst_den != 1)
+ return 0;
+
+ return 1;
+}
+
+static int imf_seek(AVFormatContext *s, int stream_index, int64_t min_ts,
+ int64_t ts, int64_t max_ts, int flags)
+{
+ IMFContext *c = s->priv_data;
+ uint32_t i;
+
+ if (flags & (AVSEEK_FLAG_BYTE | AVSEEK_FLAG_FRAME))
+ return AVERROR(ENOSYS);
+
+ /* rescale timestamps to Composition edit units */
+ if (stream_index < 0)
+ rescale_interval(AV_TIME_BASE_Q,
+ av_make_q(c->cpl->edit_rate.den, c->cpl->edit_rate.num),
+ &min_ts, &ts, &max_ts);
+ else
+ rescale_interval(s->streams[stream_index]->time_base,
+ av_make_q(c->cpl->edit_rate.den, c->cpl->edit_rate.num),
+ &min_ts, &ts, &max_ts);
+
+ /* requested timestamp bounds are too close */
+ if (max_ts < min_ts)
+ return -1;
+
+ /* clamp requested timestamp to provided bounds */
+ ts = FFMAX(FFMIN(ts, max_ts), min_ts);
+
+ av_log(s, AV_LOG_DEBUG, "Seeking to Composition Playlist edit unit %" PRIi64 "\n", ts);
+
+ /* set the dts of each stream and temporal offset of each track */
+ for (i = 0; i < c->track_count; i++) {
+ AVStream *st = s->streams[i];
+ IMFVirtualTrackPlaybackCtx *t = c->tracks[i];
+ int64_t dts;
+
+ if (!coherent_ts(ts, av_make_q(c->cpl->edit_rate.den, c->cpl->edit_rate.num),
+ st->time_base))
+ av_log(s, AV_LOG_WARNING, "Seek position is not coherent across tracks\n");
+
+ dts = av_rescale(ts,
+ st->time_base.den * c->cpl->edit_rate.den,
+ st->time_base.num * c->cpl->edit_rate.num);
+
+ av_log(s, AV_LOG_DEBUG, "Seeking to dts=%" PRId64 " on stream_index=%d\n",
+ dts, i);
+
+ t->current_timestamp = av_mul_q(av_make_q(dts, 1), st->time_base);
+ if (t->current_resource_index >= 0) {
+ avformat_close_input(&t->resources[t->current_resource_index].ctx);
+ t->current_resource_index = -1;
+ }
+ }
+
+ return 0;
+}
+
static const AVOption imf_options[] = {
{
.name = "assetmaps",
@@ -966,7 +1040,7 @@ static const AVClass imf_class = {
const AVInputFormat ff_imf_demuxer = {
.name = "imf",
.long_name = NULL_IF_CONFIG_SMALL("IMF (Interoperable Master Format)"),
- .flags = AVFMT_EXPERIMENTAL,
+ .flags = AVFMT_EXPERIMENTAL | AVFMT_NO_BYTE_SEEK,
.flags_internal = FF_FMT_INIT_CLEANUP,
.priv_class = &imf_class,
.priv_data_size = sizeof(IMFContext),
@@ -974,4 +1048,5 @@ const AVInputFormat ff_imf_demuxer = {
.read_header = imf_read_header,
.read_packet = imf_read_packet,
.read_close = imf_close,
+ .read_seek2 = imf_seek,
};
--
2.17.1
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