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

[Gyan Doshi]

On 17-02-2020 09:13 pm, Fu, Linjie wrote:
>> -----Original Message-----
>> From: Fu, Linjie <linjie.fu at intel.com>
>> Sent: Sunday, February 16, 2020 00:13
>> To: ffmpeg-devel at ffmpeg.org
>> Cc: Fu, Linjie <linjie.fu at intel.com>; Eoff, Ullysses A
>> <ullysses.a.eoff at intel.com>
>> Subject: [PATCH] fftools/ffmpeg_filter: add -autoscale to disable/enable the
>> default scale
>>
>> 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>
>> ---
>>   doc/ffmpeg.texi         | 16 ++++++++++++----
>>   fftools/ffmpeg.h        |  3 +++
>>   fftools/ffmpeg_filter.c |  2 +-
>>   fftools/ffmpeg_opt.c    |  5 +++++
>>   4 files changed, 21 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..a6f4216 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 +3652,9 @@ 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" },
>>
>>       /* audio options */
>>       { "aframes",        OPT_AUDIO | HAS_ARG  | OPT_PERFILE | OPT_OUTPUT,
>> { .func_arg = opt_audio_frames },
>> --
>> 2.7.4

What happens if user disables autoscale and the frame sizes do vary but 
the encoder doesn't support changing props?

Gyan