[FFmpeg-devel] [PATCH 1/8] lavf: add a flag to enable/disable automatic bitstream filtering

[Rodger Combs]

This is mostly useful for muxers that wrap other muxers, such as dashenc
and segment. The actual duplicated bitstream filtering is largely harmless,
but delaying the header can cause problems when the muxer intended the header
to be written to a separate file.
---
 libavformat/avformat.h      | 1 +
 libavformat/mux.c           | 4 ++--
 libavformat/options_table.h | 3 ++-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 5e918a0..3b41b57 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1434,6 +1434,7 @@ 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_AUTO_BSF    0x100000 ///< Wait for packet data before writing a header, and add bitstream filters as requested by the muxer
 
     /**
      * Maximum size of the data read from input for determining
diff --git a/libavformat/mux.c b/libavformat/mux.c
index 9ca5df4..52dfc09 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -455,7 +455,7 @@ int avformat_write_header(AVFormatContext *s, AVDictionary **options)
     if ((ret = init_muxer(s, options)) < 0)
         return ret;
 
-    if (s->oformat->write_header && !s->oformat->check_bitstream) {
+    if (s->oformat->write_header && !(s->oformat->check_bitstream && s->flags & AVFMT_FLAG_AUTO_BSF)) {
         ret = s->oformat->write_header(s);
         if (ret >= 0 && s->pb && s->pb->error < 0)
             ret = s->pb->error;
@@ -1025,7 +1025,7 @@ int av_interleaved_write_frame(AVFormatContext *s, AVPacket *pkt)
     if (pkt) {
         AVStream *st = s->streams[pkt->stream_index];
 
-        if (s->oformat->check_bitstream) {
+        if (s->oformat->check_bitstream && s->flags & AVFMT_FLAG_AUTO_BSF) {
             if (!st->internal->bitstream_checked) {
                 if ((ret = s->oformat->check_bitstream(s, pkt)) < 0)
                     goto fail;
diff --git a/libavformat/options_table.h b/libavformat/options_table.h
index 0be5221..235cd01 100644
--- a/libavformat/options_table.h
+++ b/libavformat/options_table.h
@@ -39,7 +39,7 @@ static const AVOption avformat_options[] = {
 {"probesize", "set probing size", OFFSET(probesize), AV_OPT_TYPE_INT64, {.i64 = 5000000 }, 32, INT64_MAX, D},
 {"formatprobesize", "number of bytes to probe file format", OFFSET(format_probesize), AV_OPT_TYPE_INT, {.i64 = PROBE_BUF_MAX}, 0, INT_MAX-1, D},
 {"packetsize", "set packet size", OFFSET(packet_size), AV_OPT_TYPE_INT, {.i64 = DEFAULT }, 0, INT_MAX, E},
-{"fflags", NULL, OFFSET(flags), AV_OPT_TYPE_FLAGS, {.i64 = AVFMT_FLAG_FLUSH_PACKETS }, INT_MIN, INT_MAX, D|E, "fflags"},
+{"fflags", NULL, OFFSET(flags), AV_OPT_TYPE_FLAGS, {.i64 = AVFMT_FLAG_FLUSH_PACKETS | AVFMT_FLAG_AUTO_BSF }, INT_MIN, INT_MAX, D|E, "fflags"},
 {"flush_packets", "reduce the latency by flushing out packets immediately", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_FLUSH_PACKETS }, INT_MIN, INT_MAX, E, "fflags"},
 {"ignidx", "ignore index", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_IGNIDX }, INT_MIN, INT_MAX, D, "fflags"},
 {"genpts", "generate pts", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_GENPTS }, INT_MIN, INT_MAX, D, "fflags"},
@@ -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" },
+{"autobsf", "add needed bsfs automatically (delays header until each stream's first packet is written)", 0, AV_OPT_TYPE_CONST, { .i64 = AVFMT_FLAG_AUTO_BSF }, 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},
-- 
2.7.3