[FFmpeg-devel] [PATCH v2 2/3] avformat/movenc: creating producer reference time (PRFT) box
vdixit at akamai.com
vdixit at akamai.com
Mon May 7 12:57:51 EEST 2018
From: Vishwanath Dixit <vdixit at akamai.com>
The producer reference time box supplies relative wall-clock times
at which movie fragments, or files containing movie fragments
(such as segments) were produced.
The box is mainly useful in live streaming use cases. A media player
can parse the box and utilize the time fields to measure and improve
the latency during real time playout.
---
doc/muxers.texi | 10 ++++++++++
libavformat/movenc.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
libavformat/movenc.h | 9 +++++++++
3 files changed, 69 insertions(+)
diff --git a/doc/muxers.texi b/doc/muxers.texi
index 6f03bba..db81901 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -1329,6 +1329,16 @@ be negative. This enables the initial sample to have DTS/CTS of zero, and
reduces the need for edit lists for some cases such as video tracks with
B-frames. Additionally, eases conformance with the DASH-IF interoperability
guidelines.
+ at item -write_prft
+Write producer time reference box (PRFT) with a specified time source for the
+NTP field in the PRFT box. Set value as @samp{wallclock} to specify timesource
+as wallclock time and @samp{pts} to specify timesource as input packets' PTS
+values.
+
+Setting value to @samp{pts} is applicable only for a live encoding use case,
+where PTS values are set as as wallclock time at the source. For example, an
+encoding use case with decklink capture source where @option{video_pts} and
+ at option{audio_pts} are set to @samp{abs_wallclock}.
@end table
@subsection Example
diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 0b44fd6..7e616e8 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -98,6 +98,9 @@ static const AVOption options[] = {
{ "encryption_kid", "The media encryption key identifier (hex)", offsetof(MOVMuxContext, encryption_kid), AV_OPT_TYPE_BINARY, .flags = AV_OPT_FLAG_ENCODING_PARAM },
{ "use_stream_ids_as_track_ids", "use stream ids as track ids", offsetof(MOVMuxContext, use_stream_ids_as_track_ids), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM},
{ "write_tmcd", "force or disable writing tmcd", offsetof(MOVMuxContext, write_tmcd), AV_OPT_TYPE_BOOL, {.i64 = -1}, -1, 1, AV_OPT_FLAG_ENCODING_PARAM},
+ { "write_prft", "Write producer reference time box with specified time source", offsetof(MOVMuxContext, write_prft), AV_OPT_TYPE_INT, {.i64 = MOV_PRFT_NONE}, 0, MOV_PRFT_NB-1, AV_OPT_FLAG_ENCODING_PARAM, "prft"},
+ { "wallclock", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = MOV_PRFT_SRC_WALLCLOCK}, 0, 0, AV_OPT_FLAG_ENCODING_PARAM, "prft"},
+ { "pts", NULL, 0, AV_OPT_TYPE_CONST, {.i64 = MOV_PRFT_SRC_PTS}, 0, 0, AV_OPT_FLAG_ENCODING_PARAM, "prft"},
{ NULL },
};
@@ -4514,6 +4517,49 @@ static int mov_write_sidx_tags(AVIOContext *pb, MOVMuxContext *mov,
return 0;
}
+static int mov_write_prft_tag(AVIOContext *pb, MOVMuxContext *mov, int tracks)
+{
+ int64_t pos = avio_tell(pb), pts_us, ntp_ts;
+ MOVTrack *first_track;
+
+ /* PRFT should be associated with at most one track. So, choosing only the
+ * first track. */
+ if (tracks > 0)
+ return 0;
+ first_track = &(mov->tracks[0]);
+
+ if (!first_track->entry) {
+ av_log(mov->fc, AV_LOG_WARNING, "Unable to write PRFT, no entries in the track\n");
+ return 0;
+ }
+
+ if (first_track->cluster[0].pts == AV_NOPTS_VALUE) {
+ av_log(mov->fc, AV_LOG_WARNING, "Unable to write PRFT, first PTS is invalid\n");
+ return 0;
+ }
+
+ if (mov->write_prft == MOV_PRFT_SRC_WALLCLOCK) {
+ ntp_ts = ff_get_formatted_ntp_time(ff_ntp_time());
+ } else if (mov->write_prft == MOV_PRFT_SRC_PTS) {
+ pts_us = av_rescale_q(first_track->cluster[0].pts,
+ first_track->st->time_base, AV_TIME_BASE_Q);
+ ntp_ts = ff_get_formatted_ntp_time(pts_us + NTP_OFFSET_US);
+ } else {
+ av_log(mov->fc, AV_LOG_WARNING, "Unsupported PRFT box configuration: %d\n",
+ mov->write_prft);
+ return 0;
+ }
+
+ avio_wb32(pb, 0); // Size place holder
+ ffio_wfourcc(pb, "prft"); // Type
+ avio_w8(pb, 1); // Version
+ avio_wb24(pb, 0); // Flags
+ avio_wb32(pb, first_track->track_id); // reference track ID
+ avio_wb64(pb, ntp_ts); // NTP time stamp
+ avio_wb64(pb, first_track->cluster[0].pts); //media time
+ return update_size(pb, pos);
+}
+
static int mov_write_moof_tag(AVIOContext *pb, MOVMuxContext *mov, int tracks,
int64_t mdat_size)
{
@@ -4528,6 +4574,9 @@ static int mov_write_moof_tag(AVIOContext *pb, MOVMuxContext *mov, int tracks,
if (mov->flags & FF_MOV_FLAG_DASH && !(mov->flags & FF_MOV_FLAG_GLOBAL_SIDX))
mov_write_sidx_tags(pb, mov, tracks, moof_size + 8 + mdat_size);
+ if (mov->write_prft > MOV_PRFT_NONE && mov->write_prft < MOV_PRFT_NB)
+ mov_write_prft_tag(pb, mov, tracks);
+
if (mov->flags & FF_MOV_FLAG_GLOBAL_SIDX ||
!(mov->flags & FF_MOV_FLAG_SKIP_TRAILER) ||
mov->ism_lookahead) {
@@ -5317,6 +5366,7 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
trk->cluster[trk->entry].size = size;
trk->cluster[trk->entry].entries = samples_in_chunk;
trk->cluster[trk->entry].dts = pkt->dts;
+ trk->cluster[trk->entry].pts = pkt->pts;
if (!trk->entry && trk->start_dts != AV_NOPTS_VALUE) {
if (!trk->frag_discont) {
/* First packet of a new fragment. We already wrote the duration
diff --git a/libavformat/movenc.h b/libavformat/movenc.h
index c9b4072..f2967bf 100644
--- a/libavformat/movenc.h
+++ b/libavformat/movenc.h
@@ -46,6 +46,7 @@
typedef struct MOVIentry {
uint64_t pos;
int64_t dts;
+ int64_t pts;
unsigned int size;
unsigned int samples_in_chunk;
unsigned int chunkNum; ///< Chunk number if the current entry is a chunk start otherwise 0
@@ -169,6 +170,13 @@ typedef enum {
MOV_ENC_CENC_AES_CTR,
} MOVEncryptionScheme;
+typedef enum {
+ MOV_PRFT_NONE = 0,
+ MOV_PRFT_SRC_WALLCLOCK,
+ MOV_PRFT_SRC_PTS,
+ MOV_PRFT_NB
+} MOVPrftBox;
+
typedef struct MOVMuxContext {
const AVClass *av_class;
int mode;
@@ -224,6 +232,7 @@ typedef struct MOVMuxContext {
int use_stream_ids_as_track_ids;
int track_ids_ok;
int write_tmcd;
+ MOVPrftBox write_prft;
} MOVMuxContext;
#define FF_MOV_FLAG_RTP_HINT (1 << 0)
--
1.9.1
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