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lavc/movtextenc: add option to scale fontsize with height

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If the video dimensions are different than the ASS play_res then the
font sizes need to be adjusted to get the same apparent render size.

Signed-off-by: Philip Langdale <philipl@overt.org>
This commit is contained in:
John Stebbins 2020-04-05 15:02:27 -06:00 committed by Philip Langdale
parent 1f8278ee24
commit eeef870851
1 changed files with 29 additions and 1 deletions
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30
libavcodec/movtextenc.c
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@ -21,6 +21,7 @@
#include <stdarg.h>
#include "avcodec.h"
#include "libavutil/opt.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/intreadwrite.h"
@ -45,6 +46,7 @@
#define DEFAULT_STYLE_FLAG 0x00
#define BGR_TO_RGB(c) (((c) & 0xff) << 16 | ((c) & 0xff00) | (((c) >> 16) & 0xff))
#define FONTSIZE_SCALE(s,fs) ((fs) * (s)->font_scale_factor + 0.5)
#define av_bprint_append_any(buf, data, size) av_bprint_append_data(buf, ((const char*)data), size)
typedef struct {
@ -66,6 +68,7 @@ typedef struct {
} HilightcolorBox;
typedef struct {
AVClass *class;
AVCodecContext *avctx;
ASSSplitContext *ass_ctx;
@ -82,6 +85,8 @@ typedef struct {
uint16_t byte_count;
char ** fonts;
int font_count;
double font_scale_factor;
int frame_height;
} MovTextContext;
typedef struct {
@ -237,6 +242,13 @@ static int encode_sample_description(AVCodecContext *avctx)
// Populate sample description from ASS header
ass = (ASS*)s->ass_ctx;
// Compute font scaling factor based on (optionally) provided
// output video height and ASS script play_res_y
if (s->frame_height && ass->script_info.play_res_y)
s->font_scale_factor = (double)s->frame_height / ass->script_info.play_res_y;
else
s->font_scale_factor = 1;
style = ff_ass_style_get(s->ass_ctx, "Default");
if (!style && ass->styles_count) {
style = &ass->styles[0];
@ -246,7 +258,7 @@ static int encode_sample_description(AVCodecContext *avctx)
s->d.style_color = DEFAULT_STYLE_COLOR;
s->d.style_flag = DEFAULT_STYLE_FLAG;
if (style) {
s->d.style_fontsize = style->font_size;
s->d.style_fontsize = FONTSIZE_SCALE(s, style->font_size);
s->d.style_color = BGR_TO_RGB(style->primary_color & 0xffffff) << 8 |
255 - ((uint32_t)style->primary_color >> 24);
s->d.style_flag = (!!style->bold * STYLE_FLAG_BOLD) |
@ -531,6 +543,7 @@ static void mov_text_font_name_cb(void *priv, const char *name)
static void mov_text_font_size_set(MovTextContext *s, int size)
{
size = FONTSIZE_SCALE(s, size);
if (!s->style_attributes_temp ||
s->style_attributes_temp->style_fontsize == size) {
// color hasn't changed
@ -716,12 +729,27 @@ exit:
return length;
}
#define OFFSET(x) offsetof(MovTextContext, x)
#define FLAGS AV_OPT_FLAG_ENCODING_PARAM | AV_OPT_FLAG_SUBTITLE_PARAM
static const AVOption options[] = {
{ "height", "Frame height, usually video height", OFFSET(frame_height), AV_OPT_TYPE_INT, {.i64=0}, 0, INT_MAX, FLAGS },
{ NULL },
};
static const AVClass mov_text_encoder_class = {
.class_name = "MOV text enoder",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
AVCodec ff_movtext_encoder = {
.name = "mov_text",
.long_name = NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"),
.type = AVMEDIA_TYPE_SUBTITLE,
.id = AV_CODEC_ID_MOV_TEXT,
.priv_data_size = sizeof(MovTextContext),
.priv_class = &mov_text_encoder_class,
.init = mov_text_encode_init,
.encode_sub = mov_text_encode_frame,
.close = mov_text_encode_close,