[FFmpeg-devel] [PATCH] avfilter/avf_showwaves: add draw grid support

[Paul B Mahol]

On 11/21/17, Dave Rice <dave at dericed.com> wrote:
>
>> On Nov 21, 2017, at 7:36 AM, Paul B Mahol <onemda at gmail.com> wrote:
>>
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>> doc/filters.texi            |  6 ++++++
>> libavfilter/avf_showwaves.c | 28 ++++++++++++++++++++++++++++
>> 2 files changed, 34 insertions(+)
>>
>> diff --git a/doc/filters.texi b/doc/filters.texi
>> index 62f633c6f8..9c98f1684b 100644
>> --- a/doc/filters.texi
>> +++ b/doc/filters.texi
>> @@ -19178,6 +19178,12 @@ Cubic root.
>> @end table
>>
>> Default is linear.
>> +
>> + at item grid
>> +Draw grid, default is disabled.
>> +
>> + at item grid_color
>> +Set grid color.
>> @end table
>>
>> @subsection Examples
>> diff --git a/libavfilter/avf_showwaves.c b/libavfilter/avf_showwaves.c
>> index 0866967984..74d4886cd4 100644
>> --- a/libavfilter/avf_showwaves.c
>> +++ b/libavfilter/avf_showwaves.c
>> @@ -69,6 +69,8 @@ typedef struct ShowWavesContext {
>>     int mode;                   ///< ShowWavesMode
>>     int scale;                  ///< ShowWavesScale
>>     int split_channels;
>> +    int grid;
>> +    uint8_t grid_rgba[4];
>>     uint8_t *fg;
>>
>>     int (*get_h)(int16_t sample, int height);
>> @@ -104,6 +106,8 @@ static const AVOption showwaves_options[] = {
>>         { "log", "logarithmic",    0, AV_OPT_TYPE_CONST, {.i64=SCALE_LOG},
>> .flags=FLAGS, .unit="scale"},
>>         { "sqrt", "square root",   0, AV_OPT_TYPE_CONST,
>> {.i64=SCALE_SQRT}, .flags=FLAGS, .unit="scale"},
>>         { "cbrt", "cubic root",    0, AV_OPT_TYPE_CONST,
>> {.i64=SCALE_CBRT}, .flags=FLAGS, .unit="scale"},
>> +    { "grid", "draw grid", OFFSET(grid), AV_OPT_TYPE_BOOL, {.i64=0}, 0,
>> 1, FLAGS },
>> +    { "grid_color", "set grid color", OFFSET(grid_rgba),
>> AV_OPT_TYPE_COLOR, {.str="0x333300"}, 0, 0, FLAGS },
>>     { NULL }
>> };
>>
>> @@ -562,6 +566,30 @@ static int alloc_out_frame(ShowWavesContext
>> *showwaves, const int16_t *p,
>>                                           outlink->time_base);
>>         for (j = 0; j < outlink->h; j++)
>>             memset(out->data[0] + j*out->linesize[0], 0, outlink->w *
>> showwaves->pixstep);
>> +
>> +        if (showwaves->grid) {
>> +            const int pixstep = showwaves->pixstep;
>> +            int ystep = showwaves->split_channels ? outlink->h /
>> inlink->channels / 4 : outlink->h / 4;
>> +            int channels = showwaves->split_channels ? inlink->channels :
>> 1;
>> +            int x, s, c, yskip = 0;
>> +
>> +            for (c = 0; c < channels; c++) {
>> +                for (j = 0; j < 4; j++) {
>> +                    for (x = 0; x < outlink->w; x+=3) {
>> +                        for (s = 0; s < pixstep; s++) {
>> +                            out->data[0][(yskip + j * ystep) *
>> out->linesize[0] + x * pixstep + s] = showwaves->grid_rgba[s];
>> +                        }
>> +                    }
>> +                }
>> +                for (x = 0; x < outlink->w; x+=3) {
>> +                    for (s = 0; s < pixstep; s++) {
>> +                        out->data[0][(yskip + j * ystep - 1) *
>> out->linesize[0] + x * pixstep + s] = showwaves->grid_rgba[s];
>> +                    }
>> +                }
>> +
>> +                yskip += j * ystep;
>> +            }
>> +        }
>>     }
>>     return 0;
>> }
>> --
>> 2.11.0
>
> Seems interesting but do the gridlines convey any meaning? Perhaps a flags
> value too similar to waveform that should label the lines in dB or as a
> float. Also perhaps worth adjustment the placement of the gridlines
> depending on a scale (log vs lin).

That would be quite messy for log at least.
The meaning is to find out where is 0, 0.5, -0.5, -1 and 1 in linear scale.

> Dave Rice
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>