Jan Ekström:
> From: Jan Ekström <jan.ekst...@24i.com>
>
> 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.ekst...@24i.com>
> ---
> libavcodec/ttmlenc.c | 257 +++++++++++++++++++++++++++++++++++--
> libavcodec/ttmlenc.h | 3 +-
> tests/ref/fate/sub-ttmlenc | 86 +++++++------
> 3 files changed, 294 insertions(+), 52 deletions(-)
>
> diff --git a/libavcodec/ttmlenc.c b/libavcodec/ttmlenc.c
> index e3c155fdd1..7e6add62e1 100644
> --- a/libavcodec/ttmlenc.c
> +++ b/libavcodec/ttmlenc.c
> @@ -82,6 +82,7 @@ static int ttml_encode_frame(AVCodecContext *avctx, uint8_t
> *buf,
> {
> TTMLContext *s = avctx->priv_data;
> ASSDialog *dialog;
> + AVBPrint local_bprint = { 0 };
> int i;
>
> av_bprint_clear(&s->buffer);
> @@ -100,20 +101,41 @@ 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 (dialog->style) {
> + av_bprint_init(&local_bprint, 0,
> AV_BPRINT_SIZE_UNLIMITED);
> +
> + av_bprint_escape(&local_bprint, dialog->style, NULL,
> + AV_ESCAPE_MODE_XML,
> + AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
> + if (!av_bprint_is_complete(&local_bprint)) {
> + return AVERROR(ENOMEM);
> + }
>
> - if (ret < 0) {
> - av_log(avctx, log_level,
> - "Splitting received ASS dialog failed: %s\n",
> - av_err2str(ret));
> + av_bprintf(&s->buffer, "<span region=\"%s\">",
> + local_bprint.str);
>
> - if (log_level == AV_LOG_ERROR)
> - return ret;
> + av_bprint_finalize(&local_bprint, NULL);
> }
> +
> + {
> + 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 +143,22 @@ static int ttml_encode_frame(AVCodecContext *avctx,
> uint8_t *buf,
> if (!dialog)
> return AVERROR(ENOMEM);
>
> + if (dialog->style) {
> + av_bprint_init(&local_bprint, 0, AV_BPRINT_SIZE_UNLIMITED);
> +
> + av_bprint_escape(&local_bprint, dialog->style, NULL,
> + AV_ESCAPE_MODE_XML,
> + AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
> + if (!av_bprint_is_complete(&local_bprint)) {
> + return AVERROR(ENOMEM);
> + }
> +
> + av_bprintf(&s->buffer, "<span region=\"%s\">",
> + local_bprint.str);
> +
> + av_bprint_finalize(&local_bprint, NULL);
> + }
> +
> {
> int ret = ff_ass_split_override_codes(&ttml_callbacks, s,
> dialog->text);
> @@ -140,6 +178,9 @@ 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 +214,205 @@ 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;
> + }
> +}
> +
> +// 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.
> +static const char ttml_region_base[] =
> +" <region xml:id=\"%s\"\n"
> +" tts:displayAlign=\"%s\"\n"
> +" tts:textAlign=\"%s\"\n"
> +" tts:fontSize=\"%dc\"\n";
> +
> +static const char ttml_region_font_family[] =
> +" tts:fontFamily=\"%s\"\n";
> +
> +static const char ttml_region_footer[] =
> +" tts:overflow=\"visible\" />\n";
> +
> +static int ttml_write_region(AVCodecContext *avctx, AVBPrint *buf,
> + ASSStyle *style)
> +{
> + if (!style)
> + return AVERROR_INVALIDDATA;
> +
> + 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;
> + }
> +
> + {
This adds one unnecessary level of indentation. Are you worried about
the case of style == NULL?
> + const char *display_alignment =
> + ttml_get_display_alignment(style->alignment);
> + const char *text_alignment =
> + ttml_get_text_alignment(style->alignment);
> + char *style_name = NULL;
> + char *font_name = NULL;
> + AVBPrint local_bprint = { 0 };
An AVBPrint is initialized using av_bprint_init and not by zeroing it.
Your use of this local_bprint is actually completely unnecessary: You
can just use e.g.
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");
Your usage is suboptimal even if one wanted to keep
ttml_region_font_family and ttml_region_base, because you are not using
the big advantage of AVBPrints: That one can avoid allocations if the
strings are small and their lifetime short. This would work as follows:
av_bprint_init(&local_bprint);
av_bprint_escape(&local_bprint, style->name, NULL,
AV_ESCAPE_MODE_XML,
AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
if (!av_bprint_is_complete(&local_bprint)) {
ret = AVERROR(ENOMEM);
goto fail;
}
av_bprintf(buf, ttml_region_base, local_bprint.str,
display_alignment, text_alignment, style->font_size);
if (style->font_name) {
av_bprint_clear(&local_bprint);
av_bprint_escape(&local_bprint, style->font_name, NULL,
AV_ESCAPE_MODE_XML,
AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
if (!av_bprint_is_complete(&local_bprint)) {
ret = AVERROR(ENOMEM);
goto fail;
}
av_bprintf(buf, ttml_region_font_family, local_bprint.str);
}
av_bprintf(buf, ttml_region_footer);
ret = 0;
fail:
av_bprint_finalize(&local_bprint, NULL);
return ret;
> + int ret = AVERROR_BUG;
> +
> + 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_bprint_init(&local_bprint, 0, AV_BPRINT_SIZE_UNLIMITED);
> + av_bprint_escape(&local_bprint, style->name, NULL,
> + AV_ESCAPE_MODE_XML,
> AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
> + if (!av_bprint_is_complete(&local_bprint)) {
Potential memleak here.
> + return AVERROR(ENOMEM);
> + }
> +
> + if ((ret = av_bprint_finalize(&local_bprint, &style_name)) < 0)
> + return ret;
> +
> + av_bprintf(buf, ttml_region_base, style_name,
> + display_alignment, text_alignment, style->font_size);
> +
> + if (style->font_name) {
> + av_bprint_init(&local_bprint, 0, AV_BPRINT_SIZE_UNLIMITED);
> + av_bprint_escape(&local_bprint, style->font_name, NULL,
> + AV_ESCAPE_MODE_XML,
> AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
> + if (!av_bprint_is_complete(&local_bprint)) {
> + ret = AVERROR(ENOMEM);
> + goto fail;
Potential leak here.
> + }
> +
> + if ((ret = av_bprint_finalize(&local_bprint, &font_name)) < 0)
> + goto fail;
> +
> + av_bprintf(buf, ttml_region_font_family, font_name);
> + }
> +
> +
> + av_bprintf(buf, ttml_region_footer);
> +
> + ret = 0;
> +
> +fail:
> + av_freep(&style_name);
> + av_freep(&font_name);
> + return ret;
> + }
> +}
> +
> 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;
> + ASSStyle *style = ff_ass_style_get(s->ass_ctx, "Default");
Seems unused.
> +
> + if (!script_info.play_res_x || script_info.play_res_x < 0 ||
> + !script_info.play_res_y || 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 = AVERROR_BUG;
> + style = &ass->styles[i];
> +
> + if ((ret = ttml_write_region(avctx, &s->buffer, style)) < 0)
> + return ret;
> + }
> +
> + av_bprintf(&s->buffer, " </layout>\n");
> + av_bprintf(&s->buffer, " </head>\n");
> +
> + if (!av_bprint_is_complete(&s->buffer)) {
> return AVERROR(ENOMEM);
> }
>
> - avctx->extradata_size = TTMLENC_EXTRADATA_SIGNATURE_SIZE;
> + additional_extradata_size = s->buffer.len;
> +
> + // and now, write the contents of the AVB
> + 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;
> }
>
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