[FFmpeg-devel] [PATCH] ffmpeg: add per-stream input option drop_changed

[Gyan Doshi <ffmpeg@gyani.pro>]

This is a replacement in ffmpeg for the deprecated avcodec flag AV_CODEC_FLAG_DROPCHANGED.

This option is meant to be used when the filtergraph should not be
reinited upon input parameter changes as that leads to loss of state
in the filtergraph potentially leading to broken or aborted output,
e.g. inserting of silence with first_pts specified in aresample.

Generally useful to avoid corrupted yet decodable packets in live
streaming inputs.

This option when enabled takes precedence over reinit_filters
---
 doc/ffmpeg.texi         |  6 ++++++
 fftools/ffmpeg.h        |  2 ++
 fftools/ffmpeg_demux.c  | 13 ++++++++++++-
 fftools/ffmpeg_filter.c | 10 ++++++++++
 fftools/ffmpeg_opt.c    |  3 +++
 5 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
index fca220a334..a73db79f94 100644
--- a/doc/ffmpeg.texi
+++ b/doc/ffmpeg.texi
@@ -1373,6 +1373,12 @@ The properties where a change triggers reinitialization are,
 for video, frame resolution or pixel format;
 for audio, sample format, sample rate, channel count or channel layout.
 
+@item -drop_changed[:@var{stream_specifier}] @var{integer} (@emph{input,per-stream})
+This boolean option determines whether a frame with differing frame parameters mid-stream
+gets dropped instead of leading to filtergraph reinitialization, as that would lead to loss
+of filter state. Generally useful to avoid corrupted yet decodable packets in live streaming
+inputs. Default is false.
+
 @item -filter_threads @var{nb_threads} (@emph{global})
 Defines how many threads are used to process a filter pipeline. Each pipeline
 will produce a thread pool with this many threads available for parallel processing.
diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index 86a3e10c6b..5869979214 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -232,6 +232,7 @@ typedef struct OptionsContext {
     SpecifierOptList filter_scripts;
 #endif
     SpecifierOptList reinit_filters;
+    SpecifierOptList drop_changed;
     SpecifierOptList fix_sub_duration;
     SpecifierOptList fix_sub_duration_heartbeat;
     SpecifierOptList canvas_sizes;
@@ -262,6 +263,7 @@ enum IFilterFlags {
     IFILTER_FLAG_REINIT         = (1 << 1),
     IFILTER_FLAG_CFR            = (1 << 2),
     IFILTER_FLAG_CROP           = (1 << 3),
+    IFILTER_FLAG_DROPCHANGED    = (1 << 4),
 };
 
 typedef struct InputFilterOptions {
diff --git a/fftools/ffmpeg_demux.c b/fftools/ffmpeg_demux.c
index b8171e336e..292b718f14 100644
--- a/fftools/ffmpeg_demux.c
+++ b/fftools/ffmpeg_demux.c
@@ -67,6 +67,7 @@ typedef struct DemuxStream {
     int                      reinit_filters;
     int                      autorotate;
     int                      apply_cropping;
+    int                      drop_changed;
 
 
     int                      wrap_correction_done;
@@ -1099,7 +1100,8 @@ int ist_filter_add(InputStream *ist, InputFilter *ifilter, int is_simple,
         return AVERROR(ENOMEM);
 
     opts->flags |= IFILTER_FLAG_AUTOROTATE * !!(ds->autorotate) |
-                   IFILTER_FLAG_REINIT     * !!(ds->reinit_filters);
+                   IFILTER_FLAG_REINIT     * !!(ds->reinit_filters) |
+                   IFILTER_FLAG_DROPCHANGED* !!(ds->drop_changed);
 
     return 0;
 }
@@ -1410,6 +1412,15 @@ static int ist_add(const OptionsContext *o, Demuxer *d, AVStream *st, AVDictiona
     ds->reinit_filters = -1;
     opt_match_per_stream_int(ist, &o->reinit_filters, ic, st, &ds->reinit_filters);
 
+    ds->drop_changed = 0;
+    opt_match_per_stream_int(ist, &o->drop_changed, ic, st, &ds->drop_changed);
+
+    if (ds->drop_changed && ds->reinit_filters) {
+        if (ds->reinit_filters > 0)
+            av_log(ist, AV_LOG_ERROR, "drop_changed and reinit_filters both set, which is contradictory; ignoring reinit_filters.\n");
+        ds->reinit_filters = 0;
+    }
+
     ist->user_set_discard = AVDISCARD_NONE;
 
     if ((o->video_disable && ist->st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) ||
diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
index ef35c3988f..fddfbceec1 100644
--- a/fftools/ffmpeg_filter.c
+++ b/fftools/ffmpeg_filter.c
@@ -126,6 +126,7 @@ typedef struct InputFilterPriv {
 
     int                 eof;
     int                 bound;
+    uint64_t            nb_dropped;
 
     // parameters configured for this input
     int                 format;
@@ -2898,6 +2899,13 @@ static int send_frame(FilterGraph *fg, FilterGraphThread *fgt,
     } else if (ifp->downmixinfo_present)
         need_reinit |= DOWNMIX_CHANGED;
 
+    if (need_reinit && (ifp->opts.flags & IFILTER_FLAG_DROPCHANGED)) {
+            ifp->nb_dropped++;
+            av_log(fg, AV_LOG_DEBUG, "Avoiding reinit; dropping frame pts: %s bound for %s\n", av_ts2str(frame->pts), ifilter->name);
+            av_frame_unref(frame);
+            return 0;
+    }
+
     if (!(ifp->opts.flags & IFILTER_FLAG_REINIT) && fgt->graph)
         need_reinit = 0;
 
@@ -3140,6 +3148,8 @@ read_frames:
         ret = read_frames(fg, &fgt, fgt.frame);
         if (ret == AVERROR_EOF) {
             av_log(fg, AV_LOG_VERBOSE, "All consumers returned EOF\n");
+            if (ifp->opts.flags & IFILTER_FLAG_DROPCHANGED)
+                av_log(fg, AV_LOG_VERBOSE, "Total changed input frames dropped : %"PRId64"\n", ifp->nb_dropped);
             break;
         } else if (ret < 0) {
             av_log(fg, AV_LOG_ERROR, "Error sending frames to consumers: %s\n",
diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
index 1f5e6050c8..6ec325f51e 100644
--- a/fftools/ffmpeg_opt.c
+++ b/fftools/ffmpeg_opt.c
@@ -1718,6 +1718,9 @@ const OptionDef options[] = {
     { "reinit_filter",          OPT_TYPE_INT, OPT_PERSTREAM | OPT_INPUT | OPT_EXPERT,
         { .off = OFFSET(reinit_filters) },
         "reinit filtergraph on input parameter changes", "" },
+    { "drop_changed",          OPT_TYPE_INT, OPT_PERSTREAM | OPT_INPUT | OPT_EXPERT,
+        { .off = OFFSET(drop_changed) },
+        "drop frame instead of reiniting filtergraph on input parameter changes", "" },
     { "filter_complex",         OPT_TYPE_FUNC, OPT_FUNC_ARG | OPT_EXPERT,
         { .func_arg = opt_filter_complex },
         "create a complex filtergraph", "graph_description" },
-- 
2.46.1

_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email
ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".