On Mon, 6 Apr 2020 11:52:18 -0600
John Stebbins <jstebb...@jetheaddev.com> wrote:
> 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.
> ---
> libavcodec/movtextenc.c | 30 +++++++++++++++++++++++++++++-
> 1 file changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/movtextenc.c b/libavcodec/movtextenc.c
> index a62bdb7eb0..3d4371b180 100644
> --- a/libavcodec/movtextenc.c
> +++ b/libavcodec/movtextenc.c
> @@ -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;
> @@ -81,6 +84,8 @@ typedef struct {
> uint16_t byte_count;
> char ** fonts;
> int font_count;
> + double font_scale_factor;
> + int frame_height;
> } MovTextContext;
>
> typedef struct {
> @@ -236,6 +241,13 @@ static int
> encode_sample_description(AVCodecContext *avctx)
> // Populate sample description from ASS header
> ass = ff_ass_get(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];
> @@ -245,7 +257,7 @@ 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) |
> @@ -530,6 +542,7 @@ 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
> @@ -709,12 +722,27 @@ 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,
LGTM.
--phil
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