[FFmpeg-soc] libavfilter audio work - qualification task
Stefano Sabatini
stefano.sabatini-lala at poste.it
Sat Apr 24 02:03:10 CEST 2010
On date Thursday 2010-04-22 17:19:16 -0700, S.N. Hemanth Meenakshisundaram encoded:
[...]
> Attached is the vf_drawtext.c and changes to libavfilter.texi (both
> are patches against libavfilter soc like you asked for)
>
> Following is the list of changes :
>
> 1. Using a single context structure now. Descriptive variable names.
>
> 2. Input parameters also are descriptive now, but sometimes
> different from the corresponding context variable where the context
> variable name is too long.
>
> 3. Using macro instead of function to parse libfreetype messages now.
>
> 4. Changed warning messages to AV_LOG_WARNINGS.
>
> 4. User now needs to provide only one of text or file, if both are
> given then file is used.
Uhmmm... this may be a source of errors so not sure it is a good idea,
I would prefer to just bail out if both options are used.
> 5. Made color string to YUV conversion separate function called for
> both fg and bg color.
>
> 6. Alignments, indents, description of filter and redundant '!='s fixed.
>
> 7. Reading file only once now in init.
>
> 8. Using re-entrant localtime_r now.
>
> 9. The documentation now uses $var{x} instead of ``x''. Made these
> changes throughout the libavfilter doc, not just drawtext. Is that
> ok?
Mmh no we're pretty strict about this, don't worry about the others
I'll fix them tomorrow if I won't be too lazy.
> 10. Updated documentation with new parameter names, strftime
> behavior and the file/text requirement.
Note: the strfmt syntax may be extended, for example it would be
rather useful to be able to print some of the information about the
frame/link, e.g. PTS, number of frame, format, size, etc.,
this may be done eventually in a further patch...
> As for the alpha channel support in drawbox function, do we need to
> update the alpha values? Should the caller be allowed to specify
> bgcolor or fgcolor in #RRGGBBAA format?
Why not? That would be cool don't you agree? ;-) If looks not trivial
skip it, that may be eventually added in a further patch.
> Please review and let me know if there's anything else that needs to
> be fixed.
>
> Regards,
> Hemanth
> Index: vf_drawtext.c
> ===================================================================
> --- vf_drawtext.c (revision 0)
> +++ vf_drawtext.c (revision 0)
> @@ -0,0 +1,476 @@
> +/*
> + * copyright (c) 2010 S.N. Hemanth Meenakshisundaram
> + * Original vhook author: Gustavo Sverzut Barbieri <gsbarbieri at yahoo.com.br>
> + * Libavfilter version : S.N. Hemanth Meenakshisundaram <smeenaks at ucsd.edu>
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * Drawtext Filter
> + */
> +
> +#include "avfilter.h"
> +#include "parseutils.h"
> +#include "libavcodec/colorspace.h"
> +#include "libavutil/pixdesc.h"
> +
> +#undef time
> +#include <sys/time.h>
> +#include <time.h>
> +
> +#include <ft2build.h>
> +#include <freetype/config/ftheader.h>
> +#include FT_FREETYPE_H
> +#include FT_GLYPH_H
> +
> +typedef struct {
> + const AVClass *class;
> + unsigned char *font;
> + unsigned char *text; ///< text to be drawn
> + char *file; ///< file with text to be drawn
> + unsigned int x; ///< x position to start drawing text
> + unsigned int y; ///< y position to start drawing text
> + unsigned int size; ///< font size to use
> + char *fgcolor_string; ///< foreground color as string
> + char *bgcolor_string; ///< background color as string
> + unsigned char fgcolor[3]; ///< foreground color in YUV
> + unsigned char bgcolor[3]; ///< background/Box color in YUV
> + short int draw_box; ///< draw box around text - true or false
> + short int outline; ///< draw outline in bg color around text
> + int text_height; ///< height of a font symbol
> + int baseline; ///< baseline to draw fonts from
> + int use_kerning; ///< font kerning is used - true/false
> + FT_Library library; ///< freetype font library handle
> + FT_Face face; ///< freetype font face handle
> + FT_Glyph glyphs[256]; ///< array holding glyphs of font
> + FT_Bitmap bitmaps[256]; ///< array holding bitmaps of font
> + int advance[256];
> + int bitmap_left[256];
> + int bitmap_top[256];
> + unsigned int glyphs_index[256];
> + int hsub, vsub; ///< chroma subsampling values
> +} DrawTextContext;
> +
> +#define OFFSET(x) offsetof(DrawTextContext, x)
> +
> +static const AVOption drawtext_options[]= {
> +{"font", "set font", OFFSET(font), FF_OPT_TYPE_STRING, 0, CHAR_MIN, CHAR_MAX },
> +{"text", "set text", OFFSET(text), FF_OPT_TYPE_STRING, 0, CHAR_MIN, CHAR_MAX },
> +{"file", "set file", OFFSET(file), FF_OPT_TYPE_STRING, 0, CHAR_MIN, CHAR_MAX },
Just an idea, file/font/text may be misleading, I suggest to use:
fontfile
textfile
text
> +{"fgcolor", "set fgcolor", OFFSET(fgcolor_string), FF_OPT_TYPE_STRING, 0, CHAR_MIN, CHAR_MAX },
set foreground color
> +{"bgcolor", "set bgcolor", OFFSET(bgcolor_string), FF_OPT_TYPE_STRING, 0, CHAR_MIN, CHAR_MAX },
same
> +{"box", "set box", OFFSET(draw_box), FF_OPT_TYPE_INT, 0, 0, 1 },
> +{"outline", "set outline", OFFSET(outline), FF_OPT_TYPE_INT, 0, 0, 1 },
> +{"size", "set size", OFFSET(size), FF_OPT_TYPE_INT, 16, 1, 72 },
"set font size"
> +{"x", "set x", OFFSET(x), FF_OPT_TYPE_INT, 0, 0, INT_MAX },
> +{"y", "set y", OFFSET(y), FF_OPT_TYPE_INT, 0, 0, INT_MAX },
> +{NULL},
> +};
> +
> +static const char *drawtext_get_name(void *ctx)
> +{
> + return "drawtext";
> +}
> +
> +static const AVClass drawtext_class = {
> + "DrawTextContext",
> + drawtext_get_name,
> + drawtext_options
> +};
> +
> +static int query_formats(AVFilterContext *ctx)
> +{
> + /* FIXME : Add support for other formats */
^
Nit++: FIXME: ...
> + enum PixelFormat pix_fmts[] = {
> + PIX_FMT_YUV420P, PIX_FMT_YUV444P, PIX_FMT_YUV422P,
> + PIX_FMT_YUV411P, PIX_FMT_YUV410P,
> + PIX_FMT_YUV440P, PIX_FMT_NONE
> + };
> +
> + avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
> + return 0;
> +}
> +
> +#undef __FTERRORS_H__
> +#define FT_ERROR_START_LIST {
> +#define FT_ERRORDEF(e, v, s) { (e), (s) },
> +#define FT_ERROR_END_LIST { 0, NULL } };
> +
> +struct ft_error
> +{
> + int err;
> + char *err_msg;
> +} ft_errors[] =
> +#include FT_ERRORS_H
> +
> +#define FT_ERRMSG(e) ft_errors[e].err_msg
> +
> +#define MAX_TEXT_SIZE 1024
> +
> +static inline int extract_color(AVFilterContext *ctx, char *color_str, unsigned char *color)
> +{
> + uint8_t rgba[4];
> + if (color_str && (av_parse_color(rgba, color_str, ctx))) {
> + return -1;
Is the color_str check necessary?
if (... && ((err = av_parse_color(...)))
return err;
> + }
> + color[0] = RGB_TO_Y(rgba[0], rgba[1], rgba[2]);
> + color[1] = RGB_TO_U(rgba[0], rgba[1], rgba[2], 0);
> + color[2] = RGB_TO_V(rgba[0], rgba[1], rgba[2], 0);
> + return 0;
> +}
> +
> +static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
> +{
> + unsigned short int c;
> + uint8_t err, file_valid = 0;
> + int y_max, y_min;
> + FT_BBox bbox;
> + DrawTextContext *dtext = ctx->priv;
> +
> + dtext->class = &drawtext_class;
> + av_opt_set_defaults2(dtext, 0, 0);
> + dtext->fgcolor_string = av_strdup("black");
> + dtext->bgcolor_string = av_strdup("white");
> +
> + if (av_set_options_string(dtext, args, "=", ":") < 0) {
I'd prefer:
if ((ret = ...) < 0) {
av_log(...)
return ret;
}
here and when we check an internal error code.
We don't know the cause of failure, it could well be a memory problem
for example, even if the provided parameter is allright.
> + av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args);
> + return AVERROR(EINVAL);
> + }
> +
> + if (!dtext->font || *(dtext->font) == 0) {
Is the second check necessary?
> + av_log(ctx, AV_LOG_ERROR, "No font file provided! (=f:filename)\n");
"(=f:filename)", that's quite confusing, make it more clear or remove that.
> + return AVERROR(EINVAL);
> + }
> +
> + if (dtext->file && *(dtext->file)) {
> + FILE *fp;
Maybe a check could be added here, if the text is already defined then
issue an error.
> + if (!(fp = fopen(dtext->file, "r"))) {
> + av_log(ctx, AV_LOG_WARNING, "WARNING: The file could not be opened.\n");
I'd skip the "WARNING" here and below, this may conflict with how the
user overrides the default log callback.
> + } else {
> + uint16_t read_bytes;
> + char *tbuff = av_malloc(MAX_TEXT_SIZE);
missing check. See the function read_file() in cmdutils.c.
> + read_bytes = fread(tbuff, sizeof(char), MAX_TEXT_SIZE-1, fp);
> + if (read_bytes > 0) {
> + tbuff[read_bytes] = 0;
> + av_free(dtext->text);
> + dtext->text = tbuff;
> + } else {
> + av_log(ctx, AV_LOG_WARNING, "WARNING: The file could not be read or\
> + is empty.\n");
Nit: dont' break the "..." string, put it on the second line.
> + av_free(tbuff);
> + }
> + fclose(fp);
> + file_valid = 1;
What's the point of file_valid?
> + }
> + }
> +
> + if (!dtext->text || *(dtext->text) == 0) {
> + av_log(ctx, AV_LOG_ERROR, "Either text or a valid file must be provided (=t:text or =f:file)\n");
> + return AVERROR(EINVAL);
> + }
> +
> + if (extract_color(ctx, dtext->fgcolor_string, dtext->fgcolor)) {
> + av_log(ctx, AV_LOG_ERROR, "Invalid foreground color: '%s'.\n", dtext->fgcolor_string);
> + return AVERROR(EINVAL);
> + }
if ((err = extract_color) < 0) {
av_log(...);
return err;
Same below.
> +
> + if (extract_color(ctx, dtext->bgcolor_string, dtext->bgcolor)) {
> + av_log(ctx, AV_LOG_ERROR, "Invalid foreground color: '%s'.\n", dtext->fgcolor_string);
^^^^ ^^
ehm..
> + return AVERROR(EINVAL);
> + }
> +
> + if ((err = FT_Init_FreeType(&(dtext->library)))) {
> + av_log(ctx, AV_LOG_ERROR, "Could not load FreeType (%s).\n", FT_ERRMSG(err));
> + return AVERROR(EINVAL);
> + }
> +
> + if ((err = FT_New_Face( dtext->library, dtext->font, 0, &(dtext->face)))) {
> + av_log(ctx, AV_LOG_ERROR, "Could not load face: %s (%s).\n", dtext->font, FT_ERRMSG(err));
> + return AVERROR(EINVAL);
> + }
> + if ((err = FT_Set_Pixel_Sizes( dtext->face, 0, dtext->size))) {
here and there spaces after/before parens, please avoid that.
> + av_log(ctx, AV_LOG_ERROR, "Could not set font size to %d pixels (%s).\n", dtext->size, FT_ERRMSG(err));
> + return AVERROR(EINVAL);
> + }
> +
> + dtext->use_kerning = FT_HAS_KERNING(dtext->face);
> +
> + /* load and cache glyphs */
> + y_max = -32000;
> + y_min = 32000;
> + /* FIXME : Supports only ASCII text now. Add Unicode support */
> + for (c=0; c <= 255; c++) {
> +
> + if (!file_valid && !strrchr(dtext->text,(unsigned char)c))
> + continue;
> +
> + /* Load char */
> + err = FT_Load_Char( dtext->face, (unsigned char) c, FT_LOAD_RENDER | FT_LOAD_MONOCHROME );
> + if (err) continue; /* ignore errors */
> +
> + dtext->bitmaps[c] = dtext->face->glyph->bitmap;
> + dtext->bitmap_left[c] = dtext->face->glyph->bitmap_left;
> + dtext->bitmap_top[c] = dtext->face->glyph->bitmap_top;
> + dtext->advance[c] = dtext->face->glyph->advance.x >> 6;
> +
> + err = FT_Get_Glyph( dtext->face->glyph, &(dtext->glyphs[c]) );
> + if (err) continue; /* ignore errors */
> + dtext->glyphs_index[c] = FT_Get_Char_Index( dtext->face, (unsigned char) c );
> +
> + /* Measure text height to calculate text_height (or the maximum text height) */
> + FT_Glyph_Get_CBox( dtext->glyphs[ c ], ft_glyph_bbox_pixels, &bbox );
> + if (bbox.yMax > y_max)
> + y_max = bbox.yMax;
> + if (bbox.yMin < y_min)
> + y_min = bbox.yMin;
> + }
> +
> + dtext->text_height = y_max - y_min;
> + dtext->baseline = y_max;
> +
> + return 0;
> +}
> +
> +static av_cold void uninit(AVFilterContext *ctx)
> +{
> + DrawTextContext *dtext = ctx->priv;
> + av_free(dtext->font);
> + av_free(dtext->text);
> + av_free(dtext->file);
> + av_free(dtext->fgcolor_string);
> + av_free(dtext->bgcolor_string);
> + FT_Done_Face(dtext->face);
> + FT_Done_FreeType(dtext->library);
> +}
> +
> +static int config_input(AVFilterLink *link)
> +{
> + DrawTextContext *dtext = link->dst->priv;
> + const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[link->format];
> + dtext->hsub = pix_desc->log2_chroma_w;
> + dtext->vsub = pix_desc->log2_chroma_h;
> + return 0;
> +}
> +
> +#define SET_PIXEL(pic_ref, yuv_color, x, y, hsub, vsub) { \
> + pic_ref->data[0][ (x ) + (y )*pic_ref->linesize[0] ] = yuv_color[0]; \
> + pic_ref->data[1][ (x >> hsub) + (y >> vsub)*pic_ref->linesize[1] ] = yuv_color[1]; \
> + pic_ref->data[2][ (x >> hsub) + (y >> vsub)*pic_ref->linesize[2] ] = yuv_color[2]; \
> +}
> +
> +#define GET_PIXEL(pic_ref, yuv_color, x, y, hsub, vsub) { \
> + yuv_color[0] = pic_ref->data[0][ (x ) + (y )*pic_ref->linesize[0] ]; \
> + yuv_color[1] = pic_ref->data[1][ (x >> hsub) + (y >> vsub)*pic_ref->linesize[1] ]; \
> + yuv_color[2] = pic_ref->data[2][ (x >> hsub) + (y >> vsub)*pic_ref->linesize[2] ]; \
> +}
> +
> +static inline void draw_glyph(AVFilterPicRef *pic_ref, FT_Bitmap *bitmap, unsigned int x,
> + unsigned int y, unsigned int width, unsigned int height,
> + unsigned char yuv_fgcolor[3], unsigned char yuv_color[3],
> + short int outline, int hsub, int vsub)
> +{
> + int r, c;
> + uint8_t spixel, dpixel[3], in_glyph=0;
> +
> + if (bitmap->pixel_mode == ft_pixel_mode_mono) {
> + in_glyph = 0;
> + for (r=0; (r < bitmap->rows) && (r+y < height); r++) {
> + for (c=0; (c < bitmap->width) && (c+x < width); c++) {
> + /* pixel in the pic_ref (destination) */
> + GET_PIXEL(pic_ref, dpixel, (c+x), (y+r), hsub, vsub);
> +
> + /* pixel in the glyph bitmap (source) */
> + spixel = bitmap->buffer[r*bitmap->pitch +c/8] & (0x80>>(c%8));
> +
> + if (spixel)
> + memcpy(dpixel, yuv_fgcolor, 3);
> +
> + if (outline) {
> + /* border detection: */
> + if ( !in_glyph && spixel ) {
> + /* left border detected */
> + in_glyph = 1;
> + /* draw left pixel border */
> + if (c-1 >= 0)
> + SET_PIXEL(pic_ref, yuv_color, (c+x-1), (y+r), hsub, vsub);
> + } else if ( in_glyph && !spixel ) {
> + /* right border detected */
> + in_glyph = 0;
> + /* 'draw' right pixel border */
> + memcpy(dpixel, yuv_color, 3);
> + }
> +
> + if (in_glyph) {
> + /* see if we have a top/bottom border */
> + /* top */
> + if ((r-1 >= 0) && (! bitmap->buffer[(r-1)*bitmap->pitch +c/8] & (0x80>>(c%8))))
> + /* we have a top border */
> + SET_PIXEL(pic_ref, yuv_color, (c+x), (y+r-1), hsub, vsub);
> +
> + /* bottom border detection */
> + if ((r+1 < height) && (! bitmap->buffer[(r+1)*bitmap->pitch +c/8] & (0x80>>(c%8))))
> + /* draw bottom border */
> + SET_PIXEL(pic_ref, yuv_color, (c+x), (y+r+1), hsub, vsub);
> + }
> + }
> + SET_PIXEL(pic_ref, dpixel, (c+x), (y+r), hsub, vsub);
> + }
> + }
> + }
> +}
> +
> +static inline void drawbox(AVFilterPicRef *pic_ref, unsigned int x, unsigned int y,
> + unsigned int width, unsigned int height,
> + unsigned char yuv_color[3], int hsub, int vsub)
> +{
> + int i, plane;
> + uint8_t *p;
> +
> + for (plane = 0; plane < 3 && pic_ref->data[plane]; plane++) {
> + int hsub1 = plane == 1 || plane == 2 ? hsub : 0;
> + int vsub1 = plane == 1 || plane == 2 ? vsub : 0;
> +
> + p = pic_ref->data[plane] + (y >> vsub1) * pic_ref->linesize[plane] + (x >> hsub1);
> + for (i = 0; i < (height >> vsub1); i++) {
> + memset(p, yuv_color[plane], (width >> hsub1));
> + p += pic_ref->linesize[plane];
> + }
> + }
> +}
Try to add alpha here.
> +
> +static void draw_text(AVFilterContext *ctx, AVFilterPicRef *pic_ref, int width, int height)
> +{
> + DrawTextContext *dtext = ctx->priv;
> + FT_Face face = dtext->face;
> + FT_GlyphSlot slot = face->glyph;
> + unsigned char *text = dtext->text;
> + unsigned char c;
> + unsigned char buff[MAX_TEXT_SIZE];
> + int x = 0, y = 0, i = 0, size = 0;
> + time_t now = time(0);
> + int str_w, str_w_max;
> + FT_Vector pos[MAX_TEXT_SIZE];
> + FT_Vector delta;
> + struct tm ltime;
> +
> + strftime(buff, sizeof(buff), text, localtime_r(&now, <ime));
Missing check on the presence of localtime_r().
> + text = buff;
> + size = strlen(text);
> +
> + /* measure text size and save glyphs position*/
> + str_w = str_w_max = 0;
> + x = dtext->x;
> + y = dtext->y;
> + for (i=0; i < size; i++) {
> + c = text[i];
> + /* kerning */
> + if ( (dtext->use_kerning) && (i > 0) && (dtext->glyphs_index[c]) ) {
> + FT_Get_Kerning(dtext->face, dtext->glyphs_index[text[i-1]],
> + dtext->glyphs_index[c], ft_kerning_default, &delta);
> + x += delta.x >> 6;
> + }
> +
> + if (( (x + dtext->advance[ c ]) >= width ) || ( c == '\n' )) {
> + if (c != '\n')
> + str_w_max = width - dtext->x - 1;
> + y += dtext->text_height;
> + x = dtext->x;
> + }
> +
> + /* save position */
> + pos[i].x = x + dtext->bitmap_left[c];
> + pos[i].y = y - dtext->bitmap_top[c] + dtext->baseline;
> + x += dtext->advance[c];
> + str_w += dtext->advance[c];
> + }
> + y += dtext->text_height;
> + if (str_w_max == 0)
> + str_w_max = str_w;
> + if (dtext->draw_box) {
> + /* Check if it doesn't pass the limits */
> + if ( str_w_max + dtext->x >= width )
> + str_w_max = width - dtext->x - 1;
> + if ( y >= height )
> + y = height - 1;
> +
> + /* Draw Background */
> + drawbox( pic_ref, dtext->x, dtext->y, str_w_max, y-dtext->y,
> + dtext->bgcolor, dtext->hsub, dtext->vsub );
> + }
> +
> + /* Draw Glyphs */
> + for (i=0; i < size; i++) {
> + c = text[i];
> +
> + /* skip '_' (consider as space) if text was specified in cmd line and
> + * skip new line char, just go to new line */
> + if (( (c == '_') && (text == dtext->text) ) || ( c == '\n' ) )
> + continue;
> +
> + /* now, draw to our target surface */
> + draw_glyph( pic_ref,
weird indent: draw_glyph(pic_ref,
also you may put more params on the same line, and save some LOC.
> + &(dtext->bitmaps[ c ]),
> + pos[i].x,
> + pos[i].y,
> + width,
> + height,
> + dtext->fgcolor,
> + dtext->bgcolor,
> + dtext->outline,
> + dtext->hsub,
> + dtext->vsub );
> +
> + /* increment pen position */
> + x += slot->advance.x >> 6;
> + }
> +}
> +
> +static void end_frame(AVFilterLink *link)
> +{
> + AVFilterLink *output = link->dst->outputs[0];
> + AVFilterPicRef *pic_ref = link->cur_pic;
> +
> + draw_text(link->dst, pic_ref, pic_ref->w, pic_ref->h);
> +
> + avfilter_draw_slice(output, 0, pic_ref->h, 1);
> + avfilter_end_frame(output);
> +}
> +
> +AVFilter avfilter_vf_drawtext = {
> + .name = "drawtext",
> + .description = "Draw text on top of video frames using libfreetype library.",
> + .priv_size = sizeof(DrawTextContext),
> + .init = init,
> + .uninit = uninit,
> +
> + .query_formats = query_formats,
> + .inputs = (AVFilterPad[]) {{ .name = "default",
> + .type = AVMEDIA_TYPE_VIDEO,
> + .get_video_buffer= avfilter_null_get_video_buffer,
> + .start_frame = avfilter_null_start_frame,
> + .end_frame = end_frame,
> + .config_props = config_input,
> + .min_perms = AV_PERM_WRITE |
> + AV_PERM_READ,
> + .rej_perms = AV_PERM_PRESERVE },
> + { .name = NULL}},
> + .outputs = (AVFilterPad[]) {{ .name = "default",
> + .type = AVMEDIA_TYPE_VIDEO, },
> + { .name = NULL}},
> +};
> --- ../../../ffmpeg_soc/libavfilter/ffmpeg/doc/libavfilter.texi 2010-04-04 02:11:17.144045518 -0700
> +++ libavfilter.texi 2010-04-22 15:07:08.367807862 -0700
> @@ -116,12 +116,12 @@
> ./ffmpeg -i in.avi -vfilters "crop=0:0:0:240" out.avi
> @end example
>
> -``x'' and ``y'' specify the position of the top-left corner of the
> +$var{x} and $var{y} specify the position of the top-left corner of the
> output (non-cropped) area.
>
> -The default value of ``x'' and ``y'' is 0.
> +The default value of $var{x} and $var{y} is 0.
>
> -The ``width'' and ``height'' parameters specify the width and height
> +The $var{width} and $var{height} parameters specify the width and height
> of the output (non-cropped) area.
>
> A value of 0 is interpreted as the maximum possible size contained in
> @@ -137,7 +137,7 @@
> 100:100 and the right-bottom corner corresponding to the right-bottom
> corner of the input image.
>
> -The default value of ``width'' and ``height'' is 0.
> +The default value of $var{width} and $var{height} is 0.
>
> @section drawbox
>
> @@ -147,6 +147,95 @@
>
> Draw a box with x:y:width:height dimensions in a chosen color.
>
> + at section drawtext
> +
> +Draws text string or text from specified file on top of video.
> +
> +It accepts the following parameters:
> +font=<font file>:text=<text>:file=<text file>:x=<x offset>:y=<y offset>:
> +fgcolor=<foreground color>:bgcolor=<background color>:size=<font size>:box=<draw box>:
> +outline=<draw outline>
I find this a little confusing, as this seems to imply that the
parameters have to be provided in a fixed order. Maybe something of
the kind:
It accepts a list of $var{key}=var{value} pairs as parameters,
separated by ":".
I bet you can write it better than me.
> +font and at least one of text and file are mandatory parameters.
> +
> +If a date/time format string is passed in place of text, the current
> +date and time are drawn in the specified format.
I don't like that "in place of". Maybe something of the type:
The filter recognizes strftime() sequences in the provided text and
expand them accordingly. Check the documentation of strftime().
[...]
Regards.
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