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avconv: make input -ss accurate when transcoding

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Insert (a)trim filters on the corresponding inputs, so the extra frames
are decoded and discarded.
pull/37/head
Anton Khirnov 12 years ago
parent 56ee3f9de7
commit 811bd07846
5 changed files with 66 additions and 18 deletions
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  1. 3
      Changelog
  2. 3
      avconv.h
  3. 54
      avconv_filter.c
  4. 6
      avconv_opt.c
  5. 18
      doc/avconv.texi

3
Changelog
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@ -27,6 +27,9 @@ version 10:
- WavPack encoding through libwavpack
- Added the -n parameter to avconv
- RTMP seek support
- when transcoding with avconv (i.e. not streamcopying), -ss is now accurate
even when used as an input option. Previous behavior can be restored with
the -noaccurate_seek option.
version 9:

3
avconv.h
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@ -88,6 +88,7 @@ typedef struct OptionsContext {
/* input options */
int64_t input_ts_offset;
int rate_emu;
int accurate_seek;
SpecifierOpt *ts_scale;
int nb_ts_scale;
@ -237,9 +238,11 @@ typedef struct InputFile {
int eagain; /* true if last read attempt returned EAGAIN */
int ist_index; /* index of first stream in ist_table */
int64_t ts_offset;
int64_t start_time; /* user-specified start time in AV_TIME_BASE or AV_NOPTS_VALUE */
int nb_streams; /* number of stream that avconv is aware of; may be different
from ctx.nb_streams if new streams appear during av_read_frame() */
int rate_emu;
int accurate_seek;
#if HAVE_PTHREADS
pthread_t thread; /* thread reading from this file */

54
avconv_filter.c
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@ -173,17 +173,18 @@ static void init_input_filter(FilterGraph *fg, AVFilterInOut *in)
ist->filters[ist->nb_filters - 1] = fg->inputs[fg->nb_inputs - 1];
}
static int insert_trim(OutputStream *ost, AVFilterContext **last_filter, int *pad_idx)
static int insert_trim(int64_t start_time, int64_t duration,
AVFilterContext **last_filter, int *pad_idx,
const char *filter_name)
{
OutputFile *of = output_files[ost->file_index];
AVFilterGraph *graph = (*last_filter)->graph;
AVFilterContext *ctx;
const AVFilter *trim;
const char *name = ost->st->codec->codec_type == AVMEDIA_TYPE_VIDEO ? "trim" : "atrim";
char filter_name[128];
enum AVMediaType type = avfilter_pad_get_type((*last_filter)->output_pads, *pad_idx);
const char *name = (type == AVMEDIA_TYPE_VIDEO) ? "trim" : "atrim";
int ret = 0;
if (of->recording_time == INT64_MAX && of->start_time == AV_NOPTS_VALUE)
if (duration == INT64_MAX && start_time == AV_NOPTS_VALUE)
return 0;
trim = avfilter_get_by_name(name);
@ -193,18 +194,16 @@ static int insert_trim(OutputStream *ost, AVFilterContext **last_filter, int *pa
return AVERROR_FILTER_NOT_FOUND;
}
snprintf(filter_name, sizeof(filter_name), "%s for output stream %d:%d",
name, ost->file_index, ost->index);
ctx = avfilter_graph_alloc_filter(graph, trim, filter_name);
if (!ctx)
return AVERROR(ENOMEM);
if (of->recording_time != INT64_MAX) {
ret = av_opt_set_double(ctx, "duration", (double)of->recording_time / 1e6,
if (duration != INT64_MAX) {
ret = av_opt_set_double(ctx, "duration", (double)duration / 1e6,
AV_OPT_SEARCH_CHILDREN);
}
if (ret >= 0 && of->start_time != AV_NOPTS_VALUE) {
ret = av_opt_set_double(ctx, "start", (double)of->start_time / 1e6,
if (ret >= 0 && start_time != AV_NOPTS_VALUE) {
ret = av_opt_set_double(ctx, "start", (double)start_time / 1e6,
AV_OPT_SEARCH_CHILDREN);
}
if (ret < 0) {
@ -229,6 +228,7 @@ static int configure_output_video_filter(FilterGraph *fg, OutputFilter *ofilter,
{
char *pix_fmts;
OutputStream *ost = ofilter->ost;
OutputFile *of = output_files[ost->file_index];
AVCodecContext *codec = ost->st->codec;
AVFilterContext *last_filter = out->filter_ctx;
int pad_idx = out->pad_idx;
@ -299,7 +299,10 @@ static int configure_output_video_filter(FilterGraph *fg, OutputFilter *ofilter,
pad_idx = 0;
}
ret = insert_trim(ost, &last_filter, &pad_idx);
snprintf(name, sizeof(name), "trim for output stream %d:%d",
ost->file_index, ost->index);
ret = insert_trim(of->start_time, of->recording_time,
&last_filter, &pad_idx, name);
if (ret < 0)
return ret;
@ -313,6 +316,7 @@ static int configure_output_video_filter(FilterGraph *fg, OutputFilter *ofilter,
static int configure_output_audio_filter(FilterGraph *fg, OutputFilter *ofilter, AVFilterInOut *out)
{
OutputStream *ost = ofilter->ost;
OutputFile *of = output_files[ost->file_index];
AVCodecContext *codec = ost->st->codec;
AVFilterContext *last_filter = out->filter_ctx;
int pad_idx = out->pad_idx;
@ -370,7 +374,10 @@ static int configure_output_audio_filter(FilterGraph *fg, OutputFilter *ofilter,
pad_idx = 0;
}
ret = insert_trim(ost, &last_filter, &pad_idx);
snprintf(name, sizeof(name), "trim for output stream %d:%d",
ost->file_index, ost->index);
ret = insert_trim(of->start_time, of->recording_time,
&last_filter, &pad_idx, name);
if (ret < 0)
return ret;
@ -415,11 +422,12 @@ static int configure_input_video_filter(FilterGraph *fg, InputFilter *ifilter,
AVFilterContext *last_filter;
const AVFilter *buffer_filt = avfilter_get_by_name("buffer");
InputStream *ist = ifilter->ist;
InputFile *f = input_files[ist->file_index];
AVRational tb = ist->framerate.num ? av_inv_q(ist->framerate) :
ist->st->time_base;
AVRational sar;
char args[255], name[255];
int ret;
int ret, pad_idx = 0;
sar = ist->st->sample_aspect_ratio.num ?
ist->st->sample_aspect_ratio :
@ -452,6 +460,13 @@ static int configure_input_video_filter(FilterGraph *fg, InputFilter *ifilter,
last_filter = setpts;
}
snprintf(name, sizeof(name), "trim for input stream %d:%d",
ist->file_index, ist->st->index);
ret = insert_trim(((f->start_time == AV_NOPTS_VALUE) || !f->accurate_seek) ?
AV_NOPTS_VALUE : 0, INT64_MAX, &last_filter, &pad_idx, name);
if (ret < 0)
return ret;
if ((ret = avfilter_link(last_filter, 0, in->filter_ctx, in->pad_idx)) < 0)
return ret;
return 0;
@ -463,8 +478,9 @@ static int configure_input_audio_filter(FilterGraph *fg, InputFilter *ifilter,
AVFilterContext *last_filter;
const AVFilter *abuffer_filt = avfilter_get_by_name("abuffer");
InputStream *ist = ifilter->ist;
InputFile *f = input_files[ist->file_index];
char args[255], name[255];
int ret;
int ret, pad_idx = 0;
snprintf(args, sizeof(args), "time_base=%d/%d:sample_rate=%d:sample_fmt=%s"
":channel_layout=0x%"PRIx64,
@ -530,6 +546,14 @@ static int configure_input_audio_filter(FilterGraph *fg, InputFilter *ifilter,
last_filter = volume;
}
snprintf(name, sizeof(name), "trim for input stream %d:%d",
ist->file_index, ist->st->index);
ret = insert_trim(((f->start_time == AV_NOPTS_VALUE) || !f->accurate_seek) ?
AV_NOPTS_VALUE : 0, INT64_MAX, &last_filter, &pad_idx, name);
if (ret < 0)
return ret;
if ((ret = avfilter_link(last_filter, 0, in->filter_ctx, in->pad_idx)) < 0)
return ret;

6
avconv_opt.c
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@ -117,6 +117,7 @@ static void init_options(OptionsContext *o)
o->recording_time = INT64_MAX;
o->limit_filesize = UINT64_MAX;
o->chapters_input_file = INT_MAX;
o->accurate_seek = 1;
}
/* return a copy of the input with the stream specifiers removed from the keys */
@ -687,9 +688,11 @@ static int open_input_file(OptionsContext *o, const char *filename)
f->ctx = ic;
f->ist_index = nb_input_streams - ic->nb_streams;
f->start_time = o->start_time;
f->ts_offset = o->input_ts_offset - (copy_ts ? 0 : timestamp);
f->nb_streams = ic->nb_streams;
f->rate_emu = o->rate_emu;
f->accurate_seek = o->accurate_seek;
/* check if all codec options have been used */
unused_opts = strip_specifiers(o->g->codec_opts);
@ -2151,6 +2154,9 @@ const OptionDef options[] = {
{ "ss", HAS_ARG | OPT_TIME | OPT_OFFSET |
OPT_INPUT | OPT_OUTPUT, { .off = OFFSET(start_time) },
"set the start time offset", "time_off" },
{ "accurate_seek", OPT_BOOL | OPT_OFFSET | OPT_EXPERT |
OPT_INPUT, { .off = OFFSET(accurate_seek) },
"enable/disable accurate seeking with -ss" },
{ "itsoffset", HAS_ARG | OPT_TIME | OPT_OFFSET |
OPT_EXPERT | OPT_INPUT, { .off = OFFSET(input_ts_offset) },
"set the input ts offset", "time_off" },

18
doc/avconv.texi
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@ -265,9 +265,15 @@ Set the file size limit.
@item -ss @var{position} (@emph{input/output})
When used as an input option (before @code{-i}), seeks in this input file to
@var{position}. When used as an output option (before an output filename),
decodes but discards input until the timestamps reach @var{position}. This is
slower, but more accurate.
@var{position}. Note the in most formats it is not possible to seek exactly, so
@command{avconv} will seek to the closest seek point before @var{position}.
When transcoding and @option{-accurate_seek} is enabled (the default), this
extra segment between the seek point and @var{position} will be decoded and
discarded. When doing stream copy or when @option{-noaccurate_seek} is used, it
will be preserved.
When used as an output option (before an output filename), decodes but discards
input until the timestamps reach @var{position}.
@var{position} may be either in seconds or in @code{hh:mm:ss[.xxx]} form.
@ -834,6 +840,12 @@ This option is similar to @option{-filter_complex}, the only difference is that
its argument is the name of the file from which a complex filtergraph
description is to be read.
@item -accurate_seek (@emph{input})
This option enables or disables accurate seeking in input files with the
@option{-ss} option. It is enabled by default, so seeking is accurate when
transcoding. Use @option{-noaccurate_seek} to disable it, which may be useful
e.g. when copying some streams and transcoding the others.
@end table
@c man end OPTIONS

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