From: Luca Barbato <[email protected]> Currently ff_interleave_packet_per_dts() waits until it gets a frame for each stream before outputting packets in interleaved order.
Sparse streams (i.e. streams with much fewer packets than the other streams, like subtitles or audio with DTX) tend to add up latency and in specific cases end up allocating a large amount of memory. Emit the top packet from the packet_buffer if it has a time delta larger than a specified threshold. Original report of the issue and initial proposed solution by [email protected]. Bug-id: 31 Signed-off-by: Anton Khirnov <[email protected]> --- doc/APIchanges | 4 ++++ libavformat/avformat.h | 18 ++++++++++++++++++ libavformat/mux.c | 35 +++++++++++++++++++++++++++++++++-- libavformat/options_table.h | 1 + libavformat/version.h | 4 ++-- 5 files changed, 58 insertions(+), 4 deletions(-) diff --git a/doc/APIchanges b/doc/APIchanges index e4bd6d8..a64962b 100644 --- a/doc/APIchanges +++ b/doc/APIchanges @@ -13,6 +13,10 @@ libavutil: 2013-12-xx API changes, most recent first: +2014-02-xx - xxxxxxx - lavf 55.11.0 - avformat.h + Add AVFormatContext.sparse_stream_threshold for controlling the detection of + sparse streams. + 2014-01-xx - xxxxxxx - lavc 55.32.1 - avcodec.h Edges are not required anymore on video buffers allocated by get_buffer2() (i.e. as if the CODEC_FLAG_EMU_EDGE flag was always on). Deprecate diff --git a/libavformat/avformat.h b/libavformat/avformat.h index 00380d7..fddce00 100644 --- a/libavformat/avformat.h +++ b/libavformat/avformat.h @@ -1002,6 +1002,24 @@ typedef struct AVFormatContext { */ int debug; #define FF_FDEBUG_TS 0x0001 + + /** + * The threshold (in microseconds) for detecting sparse streams when + * interleaving -- muxing only. + * + * To ensure all the streams are interleaved correctly, + * av_interleaved_write_frame() will wait until it has at least one packet + * for each stream before actually writing any packets to the output file. + * When some streams are "sparse" (i.e. there are large gaps between + * successive packets), this can result in excessive buffering. + * + * This field specifies the maximum difference between the timestamps of the + * first and the last packet in the muxing queue, above which libavformat + * will output a packet regardless of whether it has queued a packet for all + * the streams. + */ + int64_t sparse_stream_threshold; + /***************************************************************** * All fields below this line are not part of the public API. They * may not be used outside of libavformat and can be changed and diff --git a/libavformat/mux.c b/libavformat/mux.c index 06dacea..e17019e 100644 --- a/libavformat/mux.c +++ b/libavformat/mux.c @@ -541,8 +541,39 @@ int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out, ff_interleave_add_packet(s, pkt, interleave_compare_dts); } - for (i = 0; i < s->nb_streams; i++) - stream_count += !!s->streams[i]->last_in_packet_buffer; + if (s->sparse_stream_threshold > 0 && s->packet_buffer && !flush) { + AVPacket *top_pkt = &s->packet_buffer->pkt; + int64_t delta_dts = INT64_MIN; + int64_t top_dts = av_rescale_q(top_pkt->dts, + s->streams[top_pkt->stream_index]->time_base, + AV_TIME_BASE_Q); + + for (i = 0; i < s->nb_streams; i++) { + int64_t last_dts; + const AVPacketList *last = s->streams[i]->last_in_packet_buffer; + + if (!last) + continue; + + last_dts = av_rescale_q(last->pkt.dts, + s->streams[i]->time_base, + AV_TIME_BASE_Q); + delta_dts = FFMAX(delta_dts, last_dts - top_dts); + stream_count++; + } + + if (delta_dts > s->sparse_stream_threshold) { + av_log(s, AV_LOG_DEBUG, + "Delay between the first packet and last packet in the " + "muxing queue is %"PRId64" > %"PRId64": forcing output\n", + delta_dts, s->sparse_stream_threshold); + flush = 1; + } + } else { + for (i = 0; i < s->nb_streams; i++) + stream_count += !!s->streams[i]->last_in_packet_buffer; + } + if (stream_count && (s->internal->nb_interleaved_streams == stream_count || flush)) { pktl = s->packet_buffer; diff --git a/libavformat/options_table.h b/libavformat/options_table.h index 54bf25f..b05a703 100644 --- a/libavformat/options_table.h +++ b/libavformat/options_table.h @@ -58,6 +58,7 @@ static const AVOption avformat_options[] = { {"bitstream", "detect bitstream specification deviations", 0, AV_OPT_TYPE_CONST, {.i64 = AV_EF_BITSTREAM }, INT_MIN, INT_MAX, D, "err_detect"}, {"buffer", "detect improper bitstream length", 0, AV_OPT_TYPE_CONST, {.i64 = AV_EF_BUFFER }, INT_MIN, INT_MAX, D, "err_detect"}, {"explode", "abort decoding on minor error detection", 0, AV_OPT_TYPE_CONST, {.i64 = AV_EF_EXPLODE }, INT_MIN, INT_MAX, D, "err_detect"}, +{"sparse_stream_threshold", "delay in microseconds for the stream to be considered sparse", OFFSET(sparse_stream_threshold), AV_OPT_TYPE_INT64, { .i64 = 10000000 }, 0, INT64_MAX, E }, {NULL}, }; diff --git a/libavformat/version.h b/libavformat/version.h index dbdccb4..3b96d0a 100644 --- a/libavformat/version.h +++ b/libavformat/version.h @@ -30,8 +30,8 @@ #include "libavutil/version.h" #define LIBAVFORMAT_VERSION_MAJOR 55 -#define LIBAVFORMAT_VERSION_MINOR 10 -#define LIBAVFORMAT_VERSION_MICRO 3 +#define LIBAVFORMAT_VERSION_MINOR 11 +#define LIBAVFORMAT_VERSION_MICRO 0 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \ LIBAVFORMAT_VERSION_MINOR, \ -- 1.7.10.4 _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
