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ffmpeg: add a data size threshold for muxing queue size

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This way the old max queue size limit based behavior for streams
where each individual packet is large is kept, while for smaller
streams more packets can be buffered (current default is at 50
megabytes per stream).

For some explanation, by default ffmpeg copies packets from before
the appointed seek point/start time and puts them into the local
muxing queue. Before, it getting utilized was much less likely
since as soon as the filter chain was initialized, the encoder
(and thus output stream) was also initialized.

Now, since we will be pushing the encoder initialization to when the
first AVFrame is decoded and filtered - which only happens after
the exact seek point is hit as packets are ignored until then -
this queue will be seeing much more usage.

In more layman's terms, this attempts to fix cases such as where:
- seek point ends up being 5 seconds before requested time.
- audio is set to copy, and thus immediately begins filling the
  muxing queue.
- video is being encoded, and thus all received packets are skipped
  until the requested time is hit.
This commit is contained in:
Jan Ekström 2020-10-15 21:21:05 +03:00
parent 9b45c6d74b
commit 453b2f3c15
4 changed files with 33 additions and 2 deletions
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5
doc/ffmpeg.texi
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@ -1746,6 +1746,11 @@ this buffer, in packets, for the matching output stream.
The default value of this option should be high enough for most uses, so only
touch this option if you are sure that you need it.
@item -muxing_queue_data_threshold @var{bytes} (@emph{output,per-stream})
This is a minimum threshold until which the muxing queue size is not taken into
account. Defaults to 50 megabytes per stream, and is based on the overall size
of packets passed to the muxer.
@item -auto_conversion_filters (@emph{global})
Enable automatically inserting format conversion filters in all filter
graphs, including those defined by @option{-vf}, @option{-af},

11
fftools/ffmpeg.c
View File

@ -725,8 +725,13 @@ static void write_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost, int u
AVPacket tmp_pkt = {0};
/* the muxer is not initialized yet, buffer the packet */
if (!av_fifo_space(ost->muxing_queue)) {
int new_size = FFMIN(2 * av_fifo_size(ost->muxing_queue),
ost->max_muxing_queue_size);
unsigned int are_we_over_size =
(ost->muxing_queue_data_size + pkt->size) > ost->muxing_queue_data_threshold;
int new_size = are_we_over_size ?
FFMIN(2 * av_fifo_size(ost->muxing_queue),
ost->max_muxing_queue_size) :
2 * av_fifo_size(ost->muxing_queue);
if (new_size <= av_fifo_size(ost->muxing_queue)) {
av_log(NULL, AV_LOG_ERROR,
"Too many packets buffered for output stream %d:%d.\n",
@ -741,6 +746,7 @@ static void write_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost, int u
if (ret < 0)
exit_program(1);
av_packet_move_ref(&tmp_pkt, pkt);
ost->muxing_queue_data_size += tmp_pkt.size;
av_fifo_generic_write(ost->muxing_queue, &tmp_pkt, sizeof(tmp_pkt), NULL);
return;
}
@ -2991,6 +2997,7 @@ static int check_init_output_file(OutputFile *of, int file_index)
while (av_fifo_size(ost->muxing_queue)) {
AVPacket pkt;
av_fifo_generic_read(ost->muxing_queue, &pkt, sizeof(pkt), NULL);
ost->muxing_queue_data_size -= pkt.size;
write_packet(of, &pkt, ost, 1);
}
}

11
fftools/ffmpeg.h
View File

@ -215,6 +215,8 @@ typedef struct OptionsContext {
int nb_passlogfiles;
SpecifierOpt *max_muxing_queue_size;
int nb_max_muxing_queue_size;
SpecifierOpt *muxing_queue_data_threshold;
int nb_muxing_queue_data_threshold;
SpecifierOpt *guess_layout_max;
int nb_guess_layout_max;
SpecifierOpt *apad;
@ -547,6 +549,15 @@ typedef struct OutputStream {
/* the packets are buffered here until the muxer is ready to be initialized */
AVFifoBuffer *muxing_queue;
/*
* The size of the AVPackets' buffers in queue.
* Updated when a packet is either pushed or pulled from the queue.
*/
size_t muxing_queue_data_size;
/* Threshold after which max_muxing_queue_size will be in effect */
size_t muxing_queue_data_threshold;
/* packet picture type */
int pict_type;

8
fftools/ffmpeg_opt.c
View File

@ -87,6 +87,7 @@ static const char *opt_name_canvas_sizes[] = {"canvas_size", NULL};
static const char *opt_name_pass[] = {"pass", NULL};
static const char *opt_name_passlogfiles[] = {"passlogfile", NULL};
static const char *opt_name_max_muxing_queue_size[] = {"max_muxing_queue_size", NULL};
static const char *opt_name_muxing_queue_data_threshold[] = {"muxing_queue_data_threshold", NULL};
static const char *opt_name_guess_layout_max[] = {"guess_layout_max", NULL};
static const char *opt_name_apad[] = {"apad", NULL};
static const char *opt_name_discard[] = {"discard", NULL};
@ -1564,6 +1565,11 @@ static OutputStream *new_output_stream(OptionsContext *o, AVFormatContext *oc, e
MATCH_PER_STREAM_OPT(max_muxing_queue_size, i, ost->max_muxing_queue_size, oc, st);
ost->max_muxing_queue_size *= sizeof(AVPacket);
ost->muxing_queue_data_size = 0;
ost->muxing_queue_data_threshold = 50*1024*1024;
MATCH_PER_STREAM_OPT(muxing_queue_data_threshold, i, ost->muxing_queue_data_threshold, oc, st);
if (oc->oformat->flags & AVFMT_GLOBALHEADER)
ost->enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
@ -3761,6 +3767,8 @@ const OptionDef options[] = {
{ "max_muxing_queue_size", HAS_ARG | OPT_INT | OPT_SPEC | OPT_EXPERT | OPT_OUTPUT, { .off = OFFSET(max_muxing_queue_size) },
"maximum number of packets that can be buffered while waiting for all streams to initialize", "packets" },
{ "muxing_queue_data_threshold", HAS_ARG | OPT_INT | OPT_SPEC | OPT_EXPERT | OPT_OUTPUT, { .off = OFFSET(muxing_queue_data_threshold) },
"set the threshold after which max_muxing_queue_size is taken into account", "bytes" },
/* data codec support */
{ "dcodec", HAS_ARG | OPT_DATA | OPT_PERFILE | OPT_EXPERT | OPT_INPUT | OPT_OUTPUT, { .func_arg = opt_data_codec },