[FFmpeg-devel] [PATCH 1/2] Decoding of Bold Italic and Underlined styles for 3GPP timed text subtitles
Philip Langdale
philipl at overt.org
Mon Apr 13 19:55:55 CEST 2015
On 2015-04-13 07:56, Niklesh Lalwani wrote:
> From: Niklesh <niklesh.lalwani at iitb.ac.in>
>
> This patch is a part of my qualification task to implement support for
> Bold, Italic, and Underlined style records for 3GPP timed text
> subtitles. I am continuing Wesley's work. This patch supports decoding
> of no more than one style record. Patch[2/2] attempts to use dynamic
> arrays to support multiple style records.
> Signed-off-by: Niklesh <niklesh.lalwani at iitb.ac.in>
> ---
> libavcodec/movtextdec.c | 81
> +++++++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 75 insertions(+), 6 deletions(-)
Thank you for posting this.
>
> diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
> index 1c7ffea..4e463ed 100644
> --- a/libavcodec/movtextdec.c
> +++ b/libavcodec/movtextdec.c
> @@ -26,9 +26,25 @@
> #include "libavutil/bprint.h"
> #include "libavutil/intreadwrite.h"
>
> -static int text_to_ass(AVBPrint *buf, const char *text, const char
> *text_end)
> +#define STYLE_FLAG_BOLD 1
> +#define STYLE_FLAG_ITALIC 2
> +#define STYLE_FLAG_UNDERLINE 4
> +
> +static int text_to_ass(AVBPrint *buf, const char *text, const char
> *text_end,
> + const char *style_start, const char
> *style_end,
> + const int style_flags)
> {
> - while (text < text_end) {
> + while (text < text_end) {
> + if (style_flags && text == style_start)
> + {
> + if (style_flags & STYLE_FLAG_BOLD)
> + av_bprintf(buf, "{\\b1}");
> + if (style_flags & STYLE_FLAG_ITALIC)
> + av_bprintf(buf, "{\\i1}");
> + if (style_flags & STYLE_FLAG_UNDERLINE)
> + av_bprintf(buf, "{\\u1}");
> + }
> +
> switch (*text) {
> case '\r':
> break;
> @@ -39,6 +55,16 @@ static int text_to_ass(AVBPrint *buf, const char
> *text, const char *text_end)
> av_bprint_chars(buf, *text, 1);
> break;
> }
> +
> + if (style_flags && text == style_end)
> + {
> + if (style_flags & STYLE_FLAG_BOLD)
> + av_bprintf(buf, "{\\b0}");
> + if (style_flags & STYLE_FLAG_ITALIC)
> + av_bprintf(buf, "{\\i0}");
> + if (style_flags & STYLE_FLAG_UNDERLINE)
> + av_bprintf(buf, "{\\u0}");
> + }
> text++;
> }
>
> @@ -63,6 +89,9 @@ static int mov_text_decode_frame(AVCodecContext
> *avctx,
> AVBPrint buf;
> const char *ptr = avpkt->data;
> const char *end;
> + int text_length, tsmb_type, style_entries, style_flags, tsmb_size;
> + const char *style_start, *style_end;
> + const uint8_t *tsmb;
>
> if (!ptr || avpkt->size < 2)
> return AVERROR_INVALIDDATA;
> @@ -74,6 +103,7 @@ static int mov_text_decode_frame(AVCodecContext
> *avctx,
> * already. If the value is non-zero, then it's technically a
> * bad packet.
> */
> +
> if (avpkt->size == 2)
> return AV_RB16(ptr) == 0 ? 0 : AVERROR_INVALIDDATA;
>
> @@ -82,7 +112,10 @@ static int mov_text_decode_frame(AVCodecContext
> *avctx,
> * In complex cases, there are style descriptors appended to the
> string
> * so we can't just assume the packet size is the string size.
> */
> - end = ptr + FFMIN(2 + AV_RB16(ptr), avpkt->size);
> + //end = ptr + FFMIN(2 + AV_RB16(ptr), avpkt->size);
> + text_length = AV_RB16(ptr);
> +
> + end = ptr + FFMIN(2 + text_length, avpkt->size);
> ptr += 2;
>
> ts_start = av_rescale_q(avpkt->pts,
> @@ -91,11 +124,47 @@ static int mov_text_decode_frame(AVCodecContext
> *avctx,
> ts_end = av_rescale_q(avpkt->pts + avpkt->duration,
> avctx->time_base,
> (AVRational){1,100});
> -
> + tsmb_size=0;
> // Note that the spec recommends lines be no longer than 2048
> characters.
> av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
> - text_to_ass(&buf, ptr, end);
> - ret = ff_ass_add_rect_bprint(sub, &buf, ts_start,
> ts_end-ts_start);
> + if (text_length + 2 != avpkt->size)
> + {
> + while (text_length + 2 + tsmb_size < avpkt->size)
> + {
> + tsmb = ptr + text_length+tsmb_size;
> + tsmb_size = AV_RB32(tsmb);
> + tsmb += 4;
> + tsmb_type = AV_RB32(tsmb);
> + tsmb += 4;
Remember that you need to account for large (> 32bit) boxes here. I
guess it's
almost impossible to get a large box, but it's better to be correct than
to blow
up in the future.
> +
> + if (tsmb_type == MKBETAG('s','t','y','l'))
> + {
> + style_entries = AV_RB16(tsmb);
> + tsmb += 2;
> +
> + for(int i = 0; i < style_entries;i++)
> + {
> + style_start = ptr + AV_RB16(tsmb);
> + tsmb += 2;
> + style_end = ptr + AV_RB16(tsmb);
> + tsmb += 2;
> + // fontID = AV_RB16(tsmb);
> + tsmb += 2;
> + style_flags = AV_RB8(tsmb);
> + //fontsize=AV_RB8(tsmb);
> + //tsmb += 2;
> + // text-color-rgba
> + //tsmb += 4;
> + text_to_ass(&buf, ptr, end, style_start, style_end,
> style_flags);
> + }
As we will be seeing TextModifierStyleBoxes used in multiple places, and
because it's
easier to read, please define and use a struct for it, so you don't have
to do all these
individual reads to access the information. Remember to use a packed
struct or the layout
will not match.
> + }
> +
> + }
> + }
> + else
> + text_to_ass(&buf, ptr, end, NULL, NULL, 0);
> +
> + ret = ff_ass_add_rect_bprint(sub, &buf, ts_start, ts_end -
> ts_start);
> av_bprint_finalize(&buf, NULL);
> if (ret < 0)
> return ret;
--
--phil
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