movenc: Add a min_frag_duration option

The other fragmentation options (frag_duration, frag_size and
frag_keyframe) are combined with OR, cutting fragments at the
first of the conditions being fulfilled.
Signed-off-by: Martin Storsjö <martin@martin.st>

doc/muxers.texi

@@ -172,8 +172,15 @@ Allow the caller to manually choose when to cut fragments, by
 calling @code{av_write_frame(ctx, NULL)} to write a fragment with
 the packets written so far. (This is only useful with other
 applications integrating libavformat, not from @command{avconv}.)
+@item -min_frag_duration @var{duration}
+Don't create fragments that are shorter than @var{duration} microseconds long.
 @end table
 
+If more than one condition is specified, fragments are cut when
+one of the specified conditions is fulfilled. The exception to this is
+@code{-min_frag_duration}, which has to be fulfilled for any of the other
+conditions to apply.
+
 Additionally, the way the output file is written can be adjusted
 through a few other options:
 

libavformat/movenc.c

@@ -56,6 +56,7 @@ static const AVOption options[] = {
     { "iods_audio_profile", "iods audio profile atom.", offsetof(MOVMuxContext, iods_audio_profile), AV_OPT_TYPE_INT, {.dbl = -1}, -1, 255, AV_OPT_FLAG_ENCODING_PARAM},
     { "iods_video_profile", "iods video profile atom.", offsetof(MOVMuxContext, iods_video_profile), AV_OPT_TYPE_INT, {.dbl = -1}, -1, 255, AV_OPT_FLAG_ENCODING_PARAM},
     { "frag_duration", "Maximum fragment duration", offsetof(MOVMuxContext, max_fragment_duration), AV_OPT_TYPE_INT, {.dbl = 0}, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM},
+    { "min_frag_duration", "Minimum fragment duration", offsetof(MOVMuxContext, min_fragment_duration), AV_OPT_TYPE_INT, {.dbl = 0}, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM},
     { "frag_size", "Maximum fragment size", offsetof(MOVMuxContext, max_fragment_size), AV_OPT_TYPE_INT, {.dbl = 0}, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM},
     { "ism_lookahead", "Number of lookahead entries for ISM files", offsetof(MOVMuxContext, ism_lookahead), AV_OPT_TYPE_INT, {.dbl = 0}, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM},
     { NULL },
@@ -2831,20 +2832,24 @@ static int mov_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
     unsigned int samples_in_chunk = 0;
     int size= pkt->size;
     uint8_t *reformatted_data = NULL;
+    int64_t frag_duration = 0;
 
     if (!s->pb->seekable && !(mov->flags & FF_MOV_FLAG_EMPTY_MOOV))
         return 0; /* Can't handle that */
 
     if (!size) return 0; /* Discard 0 sized packets */
 
-    if ((mov->max_fragment_duration && trk->entry &&
-         av_rescale_q(pkt->dts - trk->cluster[0].dts,
+    if (trk->entry)
+        frag_duration = av_rescale_q(pkt->dts - trk->cluster[0].dts,
                                      s->streams[pkt->stream_index]->time_base,
-                      AV_TIME_BASE_Q) >= mov->max_fragment_duration) ||
+                                     AV_TIME_BASE_Q);
+    if ((mov->max_fragment_duration &&
+         frag_duration >= mov->max_fragment_duration) ||
          (mov->max_fragment_size && mov->mdat_size + size >= mov->max_fragment_size) ||
          (mov->flags & FF_MOV_FLAG_FRAG_KEYFRAME &&
           enc->codec_type == AVMEDIA_TYPE_VIDEO &&
           trk->entry && pkt->flags & AV_PKT_FLAG_KEY)) {
+        if (frag_duration >= mov->min_fragment_duration)
             mov_flush_fragment(s);
     }
 

libavformat/movenc.h

@@ -149,6 +149,7 @@ typedef struct MOVMuxContext {
 
     int fragments;
     int max_fragment_duration;
+    int min_fragment_duration;
     int max_fragment_size;
     int ism_lookahead;
     AVIOContext *mdat_buf;