Re: [FFmpeg-devel] [PATCH] avfilter/xstack: Add support for fixed size grid

[Paul B Mahol <onemda@gmail.com>]

On Wed, Jun 29, 2022 at 9:21 AM Paul B Mahol <onemda@gmail.com> wrote:

>
>
> On Tue, Jun 28, 2022 at 9:01 PM Vignesh Venkatasubramanian <
> vigneshv-at-google.com@ffmpeg.org> wrote:
>
>> Add a short hand parameter for making a fixed size grid. The existing
>> xstack layout parameter syntax gets tedious if all one wants is a
>> matrix like grid of the input streams. Add a grid option to the xstack
>> filter that simplifies this use case by simply specifying the number of
>> rows and columns instead of specific x/y co-ordinate for each stream.
>>
>
> Use SIZE AVOption for grid size option.
> As already done in tile filter.
>

Also there is no need to always force same size of frames in grid, can
either force same width or same height.

By default it can use grid option, (just set grid default to 2x1, and
remove default layout setup thing)

>
>

>
>>
>> Also updating the filter documentation to explain the new option.
>>
>> Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
>> ---
>>  doc/filters.texi       | 19 +++++++++--
>>  libavfilter/vf_stack.c | 73 ++++++++++++++++++++++++++++++++++++------
>>  2 files changed, 81 insertions(+), 11 deletions(-)
>>
>> diff --git a/doc/filters.texi b/doc/filters.texi
>> index e525e87b3c..9d800a0fd6 100644
>> --- a/doc/filters.texi
>> +++ b/doc/filters.texi
>> @@ -24381,8 +24381,23 @@ the output video frame will be filled.
>> Similarly, videos can overlap each
>>  other if their position doesn't leave enough space for the full frame of
>>  adjoining videos.
>>
>> -For 2 inputs, a default layout of @code{0_0|w0_0} is set. In all other
>> cases,
>> -a layout must be set by the user.
>> +For 2 inputs, a default layout of @code{0_0|w0_0} is set. In all other
>> cases, a
>> +layout or a grid must be set by the user. Either grid or layout option
>> can be
>> +specified at a time. Specifying both will result in an error.
>> +
>> +@item grid
>> +Specify a fixed size grid of inputs.
>> +This option is used to create a fixed size grid of the input streams.
>> The
>> +option is of the form <rows>x<columns> (e.g. 2x4). There must be <rows> *
>> +<columns> input streams and they will be arranged as a grid with <rows>
>> rows and
>> +<columns> columns. When using this option, all the input streams must
>> have the
>> +same width and height.
>> +
>> +Either grid or layout option can be specified at a time. Specifying both
>> will
>> +result in an error.
>> +
>> +If grid is set, then inputs option is ignored and is implicitly set to
>> +<rows>*<columns>.
>>
>>  @item shortest
>>  If set to 1, force the output to terminate when the shortest input
>> diff --git a/libavfilter/vf_stack.c b/libavfilter/vf_stack.c
>> index aa32a1bf5e..b38a193355 100644
>> --- a/libavfilter/vf_stack.c
>> +++ b/libavfilter/vf_stack.c
>> @@ -48,6 +48,9 @@ typedef struct StackContext {
>>      int is_vertical;
>>      int is_horizontal;
>>      int nb_planes;
>> +    char *grid;
>> +    int nb_grid_rows;
>> +    int nb_grid_columns;
>>      uint8_t fillcolor[4];
>>      char *fillcolor_str;
>>      int fillcolor_enable;
>> @@ -85,14 +88,6 @@ static av_cold int init(AVFilterContext *ctx)
>>      if (!strcmp(ctx->filter->name, "hstack"))
>>          s->is_horizontal = 1;
>>
>> -    s->frames = av_calloc(s->nb_inputs, sizeof(*s->frames));
>> -    if (!s->frames)
>> -        return AVERROR(ENOMEM);
>> -
>> -    s->items = av_calloc(s->nb_inputs, sizeof(*s->items));
>> -    if (!s->items)
>> -        return AVERROR(ENOMEM);
>> -
>>      if (!strcmp(ctx->filter->name, "xstack")) {
>>          if (strcmp(s->fillcolor_str, "none") &&
>>              av_parse_color(s->fillcolor, s->fillcolor_str, -1, ctx) >=
>> 0) {
>> @@ -100,7 +95,21 @@ static av_cold int init(AVFilterContext *ctx)
>>          } else {
>>              s->fillcolor_enable = 0;
>>          }
>> -        if (!s->layout) {
>> +        if (s->grid && s->layout) {
>> +            av_log(ctx, AV_LOG_ERROR, "Both layout and grid were
>> specified. Only one is allowed.\n");
>> +            return AVERROR(EINVAL);
>> +        }
>> +        if (s->grid) {
>> +            if (sscanf(s->grid, "%dx%d", &s->nb_grid_rows,
>> &s->nb_grid_columns) != 2) {
>> +                av_log(ctx, AV_LOG_ERROR, "grid string is not of the
>> form rowsxcolumns.\n");
>> +                return AVERROR(EINVAL);
>> +            }
>> +            s->nb_inputs = s->nb_grid_rows * s->nb_grid_columns;
>> +        } else {
>> +            s->nb_grid_rows = 0;
>> +            s->nb_grid_columns = 0;
>> +        }
>> +        if (!s->layout && !s->grid) {
>>              if (s->nb_inputs == 2) {
>>                  s->layout = av_strdup("0_0|w0_0");
>>                  if (!s->layout)
>> @@ -112,6 +121,15 @@ static av_cold int init(AVFilterContext *ctx)
>>          }
>>      }
>>
>> +    s->frames = av_calloc(s->nb_inputs, sizeof(*s->frames));
>> +    if (!s->frames)
>> +        return AVERROR(ENOMEM);
>> +
>> +    s->items = av_calloc(s->nb_inputs, sizeof(*s->items));
>> +    if (!s->items)
>> +        return AVERROR(ENOMEM);
>> +
>> +
>>      for (i = 0; i < s->nb_inputs; i++) {
>>          AVFilterPad pad = { 0 };
>>
>> @@ -244,6 +262,42 @@ static int config_output(AVFilterLink *outlink)
>>                  width += ctx->inputs[i]->w;
>>              }
>>          }
>> +    } else if (s->nb_grid_rows > 0 && s->nb_grid_columns > 0) {
>> +        int inw = 0, inh = 0;
>> +        int k = 0;
>> +        for (i = 0; i < s->nb_grid_rows; i++, inh += height) {
>> +            inw = 0;
>> +            for (int j = 0; j < s->nb_grid_columns; j++, k++, inw +=
>> width) {
>> +                AVFilterLink *inlink = ctx->inputs[k];
>> +                StackItem *item = &s->items[k];
>> +
>> +                if (ctx->inputs[k]->w != width) {
>> +                    av_log(ctx, AV_LOG_ERROR, "Input %d width %d does
>> not match input %d width %d.\n", k, ctx->inputs[k]->w, 0, width);
>> +                    return AVERROR(EINVAL);
>> +                }
>> +
>> +                if (ctx->inputs[k]->h != height) {
>> +                    av_log(ctx, AV_LOG_ERROR, "Input %d height %d does
>> not match input %d height %d.\n", k, ctx->inputs[k]->h, 0, height);
>> +                    return AVERROR(EINVAL);
>> +                }
>> +
>> +                if ((ret = av_image_fill_linesizes(item->linesize,
>> inlink->format, inlink->w)) < 0) {
>> +                    return ret;
>> +                }
>> +
>> +                item->height[1] = item->height[2] =
>> AV_CEIL_RSHIFT(inlink->h, s->desc->log2_chroma_h);
>> +                item->height[0] = item->height[3] = inlink->h;
>> +
>> +                if ((ret = av_image_fill_linesizes(item->x,
>> inlink->format, inw)) < 0) {
>> +                    return ret;
>> +                }
>> +
>> +                item->y[1] = item->y[2] = AV_CEIL_RSHIFT(inh,
>> s->desc->log2_chroma_h);
>> +                item->y[0] = item->y[3] = inh;
>> +            }
>> +        }
>> +        width *= s->nb_grid_columns;
>> +        height *= s->nb_grid_rows;
>>      } else {
>>          char *arg, *p = s->layout, *saveptr = NULL;
>>          char *arg2, *p2, *saveptr2 = NULL;
>> @@ -436,6 +490,7 @@ const AVFilter ff_vf_vstack = {
>>  static const AVOption xstack_options[] = {
>>      { "inputs", "set number of inputs", OFFSET(nb_inputs),
>> AV_OPT_TYPE_INT, {.i64=2}, 2, INT_MAX, .flags = FLAGS },
>>      { "layout", "set custom layout", OFFSET(layout), AV_OPT_TYPE_STRING,
>> {.str=NULL}, 0, 0, .flags = FLAGS },
>> +    { "grid", "set fixed size grid layout", OFFSET(grid),
>> AV_OPT_TYPE_STRING, {.str=NULL}, 0, 0, .flags = FLAGS },
>>      { "shortest", "force termination when the shortest input
>> terminates", OFFSET(shortest), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, .flags =
>> FLAGS },
>>      { "fill",  "set the color for unused pixels", OFFSET(fillcolor_str),
>> AV_OPT_TYPE_STRING, {.str = "none"}, .flags = FLAGS },
>>      { NULL },
>> --
>> 2.37.0.rc0.161.g10f37bed90-goog
>>
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>
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