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avcodec/ttmlenc: add initial support for regions and styles

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Attempts to utilize the TTML cell resolution as a mapping to the
reference resolution, and maps font size to cell size. Additionally
sets the display and text alignment according to the ASS alignment
number.

Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
This commit is contained in:
Jan Ekström
2021-03-29 16:34:34 +03:00
committed by Jan Ekström
parent 464d6ed98d
commit 3ef5a8ba2b
3 changed files with 245 additions and 54 deletions
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210
libavcodec/ttmlenc.c
View File

@@ -100,20 +100,33 @@ static int ttml_encode_frame(AVCodecContext *avctx, uint8_t *buf,
dialog = ff_ass_split_dialog(s->ass_ctx, ass, 0, &num);
for (; dialog && num--; dialog++) {
int ret = ff_ass_split_override_codes(&ttml_callbacks, s,
dialog->text);
int log_level = (ret != AVERROR_INVALIDDATA ||
avctx->err_recognition & AV_EF_EXPLODE) ?
AV_LOG_ERROR : AV_LOG_WARNING;
if (ret < 0) {
av_log(avctx, log_level,
"Splitting received ASS dialog failed: %s\n",
av_err2str(ret));
if (log_level == AV_LOG_ERROR)
return ret;
if (dialog->style) {
av_bprintf(&s->buffer, "<span region=\"");
av_bprint_escape(&s->buffer, dialog->style, NULL,
AV_ESCAPE_MODE_XML,
AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
av_bprintf(&s->buffer, "\">");
}
{
int ret = ff_ass_split_override_codes(&ttml_callbacks, s,
dialog->text);
int log_level = (ret != AVERROR_INVALIDDATA ||
avctx->err_recognition & AV_EF_EXPLODE) ?
AV_LOG_ERROR : AV_LOG_WARNING;
if (ret < 0) {
av_log(avctx, log_level,
"Splitting received ASS dialog failed: %s\n",
av_err2str(ret));
if (log_level == AV_LOG_ERROR)
return ret;
}
}
if (dialog->style)
av_bprintf(&s->buffer, "</span>");
}
} else {
#endif
@@ -121,6 +134,14 @@ static int ttml_encode_frame(AVCodecContext *avctx, uint8_t *buf,
if (!dialog)
return AVERROR(ENOMEM);
if (dialog->style) {
av_bprintf(&s->buffer, "<span region=\"");
av_bprint_escape(&s->buffer, dialog->style, NULL,
AV_ESCAPE_MODE_XML,
AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
av_bprintf(&s->buffer, "\">");
}
{
int ret = ff_ass_split_override_codes(&ttml_callbacks, s,
dialog->text);
@@ -140,6 +161,9 @@ static int ttml_encode_frame(AVCodecContext *avctx, uint8_t *buf,
}
}
if (dialog->style)
av_bprintf(&s->buffer, "</span>");
ff_ass_free_dialog(&dialog);
}
#if FF_API_ASS_TIMING
@@ -173,17 +197,171 @@ static av_cold int ttml_encode_close(AVCodecContext *avctx)
return 0;
}
static const char *ttml_get_display_alignment(int alignment)
{
switch (alignment) {
case 1:
case 2:
case 3:
return "after";
case 4:
case 5:
case 6:
return "center";
case 7:
case 8:
case 9:
return "before";
default:
return NULL;
}
}
static const char *ttml_get_text_alignment(int alignment)
{
switch (alignment) {
case 1:
case 4:
case 7:
return "left";
case 2:
case 5:
case 8:
return "center";
case 3:
case 6:
case 9:
return "right";
default:
return NULL;
}
}
static int ttml_write_region(AVCodecContext *avctx, AVBPrint *buf,
ASSStyle style)
{
const char *display_alignment = NULL;
const char *text_alignment = NULL;
if (!style.name) {
av_log(avctx, AV_LOG_ERROR, "Subtitle style name not set!\n");
return AVERROR_INVALIDDATA;
}
if (style.font_size < 0) {
av_log(avctx, AV_LOG_ERROR, "Invalid font size for TTML: %d!\n",
style.font_size);
return AVERROR_INVALIDDATA;
}
display_alignment = ttml_get_display_alignment(style.alignment);
text_alignment = ttml_get_text_alignment(style.alignment);
if (!display_alignment || !text_alignment) {
av_log(avctx, AV_LOG_ERROR,
"Failed to convert ASS style alignment %d of style %s to "
"TTML display and text alignment!\n",
style.alignment,
style.name);
return AVERROR_INVALIDDATA;
}
av_bprintf(buf, " <region xml:id=\"");
av_bprint_escape(buf, style.name, NULL, AV_ESCAPE_MODE_XML,
AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
av_bprintf(buf, "\"\n");
av_bprintf(buf, " tts:displayAlign=\"");
av_bprint_escape(buf, display_alignment, NULL, AV_ESCAPE_MODE_XML,
AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
av_bprintf(buf, "\"\n");
av_bprintf(buf, " tts:textAlign=\"");
av_bprint_escape(buf, text_alignment, NULL, AV_ESCAPE_MODE_XML,
AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
av_bprintf(buf, "\"\n");
// if we set cell resolution to our script reference resolution,
// then a single line is a single "point" on our canvas. Thus, by setting
// our font size to font size in cells, we should gain a similar enough
// scale without resorting to explicit pixel based font sizing, which is
// frowned upon in the TTML community.
av_bprintf(buf, " tts:fontSize=\"%dc\"\n",
style.font_size);
if (style.font_name) {
av_bprintf(buf, " tts:fontFamily=\"");
av_bprint_escape(buf, style.font_name, NULL, AV_ESCAPE_MODE_XML,
AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
av_bprintf(buf, "\"\n");
}
av_bprintf(buf, " tts:overflow=\"visible\" />\n");
return 0;
}
static int ttml_write_header_content(AVCodecContext *avctx)
{
if (!(avctx->extradata = av_mallocz(TTMLENC_EXTRADATA_SIGNATURE_SIZE +
1 + AV_INPUT_BUFFER_PADDING_SIZE))) {
TTMLContext *s = avctx->priv_data;
ASS *ass = (ASS *)s->ass_ctx;
ASSScriptInfo script_info = ass->script_info;
const size_t base_extradata_size = TTMLENC_EXTRADATA_SIGNATURE_SIZE + 1 +
AV_INPUT_BUFFER_PADDING_SIZE;
size_t additional_extradata_size = 0;
if (script_info.play_res_x <= 0 || script_info.play_res_y <= 0) {
av_log(avctx, AV_LOG_ERROR,
"Invalid subtitle reference resolution %dx%d!\n",
script_info.play_res_x, script_info.play_res_y);
return AVERROR_INVALIDDATA;
}
// write the first string in extradata, attributes in the base "tt" element.
av_bprintf(&s->buffer, ttml_default_namespacing);
// the cell resolution is in character cells, so not exactly 1:1 against
// a pixel based resolution, but as the tts:extent in the root
// "tt" element is frowned upon (and disallowed in the EBU-TT profile),
// we mimic the reference resolution by setting it as the cell resolution.
av_bprintf(&s->buffer, " ttp:cellResolution=\"%d %d\"\n",
script_info.play_res_x, script_info.play_res_y);
av_bprint_chars(&s->buffer, '\0', 1);
// write the second string in extradata, head element containing the styles
av_bprintf(&s->buffer, " <head>\n");
av_bprintf(&s->buffer, " <layout>\n");
for (int i = 0; i < ass->styles_count; i++) {
int ret = ttml_write_region(avctx, &s->buffer, ass->styles[i]);
if (ret < 0)
return ret;
}
av_bprintf(&s->buffer, " </layout>\n");
av_bprintf(&s->buffer, " </head>\n");
av_bprint_chars(&s->buffer, '\0', 1);
if (!av_bprint_is_complete(&s->buffer)) {
return AVERROR(ENOMEM);
}
avctx->extradata_size = TTMLENC_EXTRADATA_SIGNATURE_SIZE;
additional_extradata_size = s->buffer.len;
if (!(avctx->extradata =
av_mallocz(base_extradata_size + additional_extradata_size))) {
return AVERROR(ENOMEM);
}
avctx->extradata_size =
TTMLENC_EXTRADATA_SIGNATURE_SIZE + additional_extradata_size;
memcpy(avctx->extradata, TTMLENC_EXTRADATA_SIGNATURE,
TTMLENC_EXTRADATA_SIGNATURE_SIZE);
if (additional_extradata_size)
memcpy(avctx->extradata + TTMLENC_EXTRADATA_SIGNATURE_SIZE,
s->buffer.str, additional_extradata_size);
av_bprint_clear(&s->buffer);
return 0;
}

3
libavcodec/ttmlenc.h
View File

@@ -28,6 +28,7 @@
static const char ttml_default_namespacing[] =
" xmlns=\"http://www.w3.org/ns/ttml\"\n"
" xmlns:ttm=\"http://www.w3.org/ns/ttml#metadata\"\n"
" xmlns:tts=\"http://www.w3.org/ns/ttml#styling\"\n";
" xmlns:tts=\"http://www.w3.org/ns/ttml#styling\"\n"
" xmlns:ttp=\"http://www.w3.org/ns/ttml#parameter\"\n";
#endif /* AVCODEC_TTMLENC_H */