[FFmpeg-devel] [PATCH] fftools/ffmpeg_filter: add -autoscale to disable/enable the default scale

[Nicolas George]

Linjie Fu (12020-02-15):
> Currently, ffmpeg inserts scale filter by default in the filter graph
> to force the whole decoded stream to scale into the same size with the
> first frame. It's not quite make sense in resolution changing cases if
> user wants the rawvideo without any scale.
> 
> Using autoscale/noautoscale as an output option to indicate whether auto
> inserting the scale filter in the filter graph:
>     -noautoscale or -autoscale 0:
>     disable the default auto scale filter inserting.
> 
> ffmpeg -y input.mp4 out1.yuv -noautoscale out2.yuv -autoscale 0 out3.yuv
> 
> Update docs.
> 
> Signed-off-by: U. Artie Eoff <ullysses.a.eoff at intel.com>
> Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> ---
> 
> Using autoscale as an output option and fix the missing spaces.
> 
>  doc/ffmpeg.texi         | 16 ++++++++++++----
>  fftools/ffmpeg.h        |  3 +++
>  fftools/ffmpeg_filter.c |  2 +-
>  fftools/ffmpeg_opt.c    |  8 ++++++++
>  4 files changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
> index 29753f0..aebafb3 100644
> --- a/doc/ffmpeg.texi
> +++ b/doc/ffmpeg.texi
> @@ -734,10 +734,6 @@ ffmpeg -dump_attachment:t "" -i INPUT
>  Technical note -- attachments are implemented as codec extradata, so this
>  option can actually be used to extract extradata from any stream, not just
>  attachments.
> -
> - at item -noautorotate
> -Disable automatically rotating video based on file metadata.
> -
>  @end table
>  
>  @section Video Options
> @@ -819,6 +815,18 @@ Create the filtergraph specified by @var{filtergraph} and use it to
>  filter the stream.
>  
>  This is an alias for @code{-filter:v}, see the @ref{filter_option,,-filter option}.
> +
> + at item -autorotate
> +Automatically rotate the video according to file metadata. Enabled by
> +default, use @option{-noautorotate} to disable it.
> +
> + at item -autoscale
> +Automatically scale the video according to the resolution of first frame.
> +Enabled by default, use @option{-noautoscale} to disable it. When autoscale is
> +disabled, all output frames of filter graph might not be in the same resolution
> +and may be inadequate for some encoder/muxer. Therefore, it is not recommended
> +to disable it unless you really know what you are doing.
> +Disable autoscale at your own risk.
>  @end table
>  
>  @section Advanced Video options
> diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
> index 7b6f802..8beba6c 100644
> --- a/fftools/ffmpeg.h
> +++ b/fftools/ffmpeg.h
> @@ -230,6 +230,8 @@ typedef struct OptionsContext {
>      int        nb_time_bases;
>      SpecifierOpt *enc_time_bases;
>      int        nb_enc_time_bases;
> +    SpecifierOpt *autoscale;
> +    int        nb_autoscale;
>  } OptionsContext;
>  
>  typedef struct InputFilter {
> @@ -479,6 +481,7 @@ typedef struct OutputStream {
>      int force_fps;
>      int top_field_first;
>      int rotate_overridden;
> +    int autoscale;
>      double rotate_override_value;
>  
>      AVRational frame_aspect_ratio;
> diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
> index 40cc4c1..46c8ea8 100644
> --- a/fftools/ffmpeg_filter.c
> +++ b/fftools/ffmpeg_filter.c
> @@ -469,7 +469,7 @@ static int configure_output_video_filter(FilterGraph *fg, OutputFilter *ofilter,
>      if (ret < 0)
>          return ret;
>  
> -    if (ofilter->width || ofilter->height) {
> +    if ((ofilter->width || ofilter->height) && ofilter->ost->autoscale) {
>          char args[255];
>          AVFilterContext *filter;
>          AVDictionaryEntry *e = NULL;
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index 12d4488..62bcfc1 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -1405,6 +1405,8 @@ static OutputStream *new_output_stream(OptionsContext *o, AVFormatContext *oc, e
>          ost->encoder_opts  = filter_codec_opts(o->g->codec_opts, ost->enc->id, oc, st, ost->enc);
>  
>          MATCH_PER_STREAM_OPT(presets, str, preset, oc, st);
> +        ost->autoscale = 1;
> +        MATCH_PER_STREAM_OPT(autoscale, i, ost->autoscale, oc, st);
>          if (preset && (!(ret = get_preset_file_2(preset, ost->enc->name, &s)))) {
>              do  {
>                  buf = get_line(s);
> @@ -3650,6 +3652,12 @@ const OptionDef options[] = {
>      { "autorotate",       HAS_ARG | OPT_BOOL | OPT_SPEC |
>                            OPT_EXPERT | OPT_INPUT,                                { .off = OFFSET(autorotate) },
>          "automatically insert correct rotate filters" },

> +    { "autoscale",        HAS_ARG | OPT_BOOL | OPT_SPEC |
> +                          OPT_EXPERT | OPT_OUTPUT,                               { .off = OFFSET(autoscale) },
> +        "automatically insert a scale filter at the end of the filter graph if a resolution "
> +        "change is detected. This ensures all frames are the same resolution as the first frame "
> +        "when they leave the filter chain (this option is enabled by default). "
> +        "If disabled, some encoders/muxers may not support this mode."},

The help text for most options is half a line. This one is four long
lines. Maybe this is misusing the field: a short summary here, the full
explanation in the doc.

>  
>      /* audio options */
>      { "aframes",        OPT_AUDIO | HAS_ARG  | OPT_PERFILE | OPT_OUTPUT,           { .func_arg = opt_audio_frames },

Regards,

-- 
  Nicolas George
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20200215/2ef156f9/attachment.sig>