@@ -8,6 +8,9 @@ version <next>

 - ffprobe -show_programs option

 - compand filter

 - RTMP seek support

+- when transcoding with ffmpeg (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 2.0:

@@ -272,9 +272,15 @@ Set the file size limit, expressed in bytes.

 @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{ffmpeg} 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.

@@ -1060,6 +1066,12 @@ 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.

+

 @item -override_ffserver (@emph{global})

 Overrides the input specifications from ffserver. Using this option you can

 map any input stream to ffserver and control many aspects of the encoding from

@@ -93,6 +93,7 @@ typedef struct OptionsContext {

     /* input options */

     int64_t input_ts_offset;

     int rate_emu;

+    int accurate_seek;

     SpecifierOpt *ts_scale;

     int        nb_ts_scale;

@@ -282,10 +283,12 @@ typedef struct InputFile {

     int ist_index;        /* index of first stream in input_streams */

     int64_t ts_offset;

     int64_t last_ts;

+    int64_t start_time;   /* user-specified start time in AV_TIME_BASE or AV_NOPTS_VALUE */

     int nb_streams;       /* number of stream that ffmpeg is aware of; may be different

                              from ctx.nb_streams if new streams appear during av_read_frame() */

     int nb_streams_warn;  /* number of streams that the user was warned of */

     int rate_emu;

+    int accurate_seek;

 #if HAVE_PTHREADS

     pthread_t thread;           /* thread reading from this file */

@@ -276,21 +276,22 @@ 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;

     // Use with duration and without output starttime is buggy with trim filters

-    if (of->start_time == AV_NOPTS_VALUE)

+    if (start_time == AV_NOPTS_VALUE)

         return 0;

     trim = avfilter_get_by_name(name);

@@ -300,18 +301,16 @@ 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) {

@@ -336,6 +335,7 @@ 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;

@@ -408,7 +408,10 @@ 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;

@@ -422,9 +425,9 @@ 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;

-    OutputFile *of = output_files[ost->file_index];

     int pad_idx = out->pad_idx;

     char *sample_fmts, *sample_rates, *channel_layouts;

     char name[255];

@@ -534,7 +537,10 @@ static int configure_output_audio_filter(FilterGraph *fg, OutputFilter *ofilter,

         }

     }

-    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;

@@ -615,13 +621,14 @@ 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 fr = ist->framerate;

     AVRational sar;

     AVBPrint args;

     char name[255];

-    int ret;

+    int ret, pad_idx = 0;

     if (!fr.num)

         fr = av_guess_frame_rate(input_files[ist->file_index]->ctx, ist->st, NULL);

@@ -688,6 +695,13 @@ static int configure_input_video_filter(FilterGraph *fg, InputFilter *ifilter,

         last_filter = yadif;

     }

+    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;

@@ -699,9 +713,10 @@ 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];

     AVBPrint args;

     char name[255];

-    int ret;

+    int ret, pad_idx = 0;

     av_bprint_init(&args, 0, AV_BPRINT_SIZE_AUTOMATIC);

     av_bprintf(&args, "time_base=%d/%d:sample_rate=%d:sample_fmt=%s",

@@ -776,6 +791,14 @@ static int configure_input_audio_filter(FilterGraph *fg, InputFilter *ifilter,

         snprintf(args, sizeof(args), "%f", audio_volume / 256.);

         AUTO_INSERT_FILTER_INPUT("-vol", "volume", args);

     }

+

+    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;

@@ -150,6 +150,7 @@ static void init_options(OptionsContext *o, int is_input)

     o->start_time     = AV_NOPTS_VALUE;

     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 */

@@ -853,9 +854,11 @@ 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);

@@ -2619,6 +2622,9 @@ 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" },