[FFmpeg-devel] avformat/mux: implement AVFMT_FLAG_SHORTEST

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index d8a6cf3..eecae9f 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1448,6 +1448,7 @@  typedef struct AVFormatContext {
 #define AVFMT_FLAG_PRIV_OPT    0x20000 ///< Enable use of private options by delaying codec open (this could be made default once all code is converted)
 #define AVFMT_FLAG_KEEP_SIDE_DATA 0x40000 ///< Don't merge side data but keep it separate.
 #define AVFMT_FLAG_FAST_SEEK   0x80000 ///< Enable fast, but inaccurate seeks for some formats
+#define AVFMT_FLAG_SHORTEST   0x100000 ///< Stop muxing when the shortest stream stops.
 
     /**
      * Maximum size of the data read from input for determining
diff --git a/libavformat/internal.h b/libavformat/internal.h
index 0119749..b77f114 100644
--- a/libavformat/internal.h
+++ b/libavformat/internal.h
@@ -125,6 +125,11 @@  struct AVFormatInternal {
      */
     int header_written;
     int write_header_ret;
+
+    /**
+     * Timestamp of the end of the shortest stream.
+     */
+    int64_t shortest_end;
 };
 
 struct AVStreamInternal {
diff --git a/libavformat/mux.c b/libavformat/mux.c
index e9973ed..493d656 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -1040,7 +1040,7 @@  int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out,
     }
 
     if (s->internal->nb_interleaved_streams == stream_count)
-        flush = 1;
+        flush = 2;
 
     if (s->max_interleave_delta > 0 &&
         s->internal->packet_buffer &&
@@ -1075,6 +1075,44 @@  int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out,
         }
     }
 
+    if (s->internal->packet_buffer &&
+        flush == 1 &&
+        (s->flags & AVFMT_FLAG_SHORTEST) &&
+        s->internal->shortest_end == AV_NOPTS_VALUE) {
+        AVPacket *top_pkt = &s->internal->packet_buffer->pkt;
+
+        s->internal->shortest_end = av_rescale_q(top_pkt->dts,
+                                       s->streams[top_pkt->stream_index]->time_base,
+                                       AV_TIME_BASE_Q);
+    }
+
+    if (s->internal->shortest_end != AV_NOPTS_VALUE) {
+        while (s->internal->packet_buffer) {
+            AVPacket *top_pkt = &s->internal->packet_buffer->pkt;
+            AVStream *st;
+            int64_t top_dts = av_rescale_q(top_pkt->dts,
+                                        s->streams[top_pkt->stream_index]->time_base,
+                                        AV_TIME_BASE_Q);
+
+            if (s->internal->shortest_end + 1 >= top_dts)
+                break;
+
+            pktl = s->internal->packet_buffer;
+            st   = s->streams[pktl->pkt.stream_index];
+
+            s->internal->packet_buffer = pktl->next;
+            if (!s->internal->packet_buffer)
+                s->internal->packet_buffer_end = NULL;
+
+            if (st->last_in_packet_buffer == pktl)
+                st->last_in_packet_buffer = NULL;
+
+            av_packet_unref(&pktl->pkt);
+            av_freep(&pktl);
+            flush = 0;
+        }
+    }
+
     if (stream_count && flush) {
         AVStream *st;
         pktl = s->internal->packet_buffer;
diff --git a/libavformat/options.c b/libavformat/options.c
index 04d9c45..25a506e 100644
--- a/libavformat/options.c
+++ b/libavformat/options.c
@@ -143,6 +143,7 @@  AVFormatContext *avformat_alloc_context(void)
     }
     ic->internal->offset = AV_NOPTS_VALUE;
     ic->internal->raw_packet_buffer_remaining_size = RAW_PACKET_BUFFER_SIZE;
+    ic->internal->shortest_end = AV_NOPTS_VALUE;
 
     return ic;
 }
diff --git a/libavformat/options_table.h b/libavformat/options_table.h
index 3b74d1b..699809a 100644
--- a/libavformat/options_table.h
+++ b/libavformat/options_table.h
@@ -54,6 +54,7 @@  static const AVOption avformat_options[] = {
 {"nobuffer", "reduce the latency introduced by optional buffering", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_NOBUFFER }, 0, INT_MAX, D, "fflags"},
 {"seek2any", "allow seeking to non-keyframes on demuxer level when supported", OFFSET(seek2any), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, D},
 {"bitexact", "do not write random/volatile data", 0, AV_OPT_TYPE_CONST, { .i64 = AVFMT_FLAG_BITEXACT }, 0, 0, E, "fflags" },
+{"shortest", "stop muxing with the shortest stream", 0, AV_OPT_TYPE_CONST, { .i64 = AVFMT_FLAG_SHORTEST }, 0, 0, E, "fflags" },
 {"analyzeduration", "specify how many microseconds are analyzed to probe the input", OFFSET(max_analyze_duration), AV_OPT_TYPE_INT64, {.i64 = 0 }, 0, INT64_MAX, D},
 {"cryptokey", "decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, {.dbl = 0}, 0, 0, D},
 {"indexmem", "max memory used for timestamp index (per stream)", OFFSET(max_index_size), AV_OPT_TYPE_INT, {.i64 = 1<<20 }, 0, INT_MAX, D},