[FFmpeg-devel] [PATCH 2/2] Encoding of styles - Bold, Italic, Underlined for timed-text subttiles

Niklesh Lalwani niklesh.lalwani at iitb.ac.in
Thu Jun 11 07:09:12 CEST 2015


Tested on QuickTime 10.3 on OSX, and VLC. For some reason, it doesn't work
on Quicktime Windows, I can't figure out why.

Thanks,

Niklesh


On Thu, Jun 11, 2015 at 10:18 AM, Niklesh Lalwani <
niklesh.lalwani at iitb.ac.in> wrote:

> From: Niklesh <niklesh.lalwani at iitb.ac.in>
>
> Encoding of bold, Italic, underlined styles for 3gpp timed text subtitles.
> All the formatting information is appended into the buffer after the text,
> unlike other encoders like srt, which can write out styling information as
> it goes. Another tricky part is to take care of the Endianness properly
> while writing into the buffer.
>
> Signed-off-by: Niklesh <niklesh.lalwani at iitb.ac.in>
> ---
>  libavcodec/movtextenc.c | 104
> +++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 76 insertions(+), 28 deletions(-)
>
> diff --git a/libavcodec/movtextenc.c b/libavcodec/movtextenc.c
> index 1b8f454..adbe19d 100644
> --- a/libavcodec/movtextenc.c
> +++ b/libavcodec/movtextenc.c
> @@ -24,14 +24,27 @@
>  #include "libavutil/avassert.h"
>  #include "libavutil/avstring.h"
>  #include "libavutil/intreadwrite.h"
> +#include "libavutil/common.h"
>  #include "ass_split.h"
>  #include "ass.h"
>
> +#define STYLE_FLAG_BOLD         1
> +#define STYLE_FLAG_ITALIC       2
> +#define STYLE_FLAG_UNDERLINE    4
> +
>  typedef struct {
>      ASSSplitContext *ass_ctx;
> -    char buffer[2048];
> -    char *ptr;
> -    char *end;
> +    AVBPrint buffer;
> +    uint32_t tsmb_size;
> +    uint32_t tsmb_type;
> +    uint16_t style_entries;
> +    uint16_t style_start;
> +    uint16_t style_end;
> +    uint16_t style_fontID;
> +    uint8_t style_flag;
> +    uint8_t style_fontsize;
> +    uint32_t style_color;
> +    uint16_t text_pos;
>  } MovTextContext;
>
>
> @@ -47,10 +60,10 @@ static av_cold int mov_text_encode_init(AVCodecContext
> *avctx)
>          0xFF,                   // int8_t vertical-justification
>          0x00, 0x00, 0x00, 0x00, // uint8_t background-color-rgba[4]
>          // BoxRecord {
> -        0x00, 0x00,             // int16_t top
> -        0x00, 0x00,             // int16_t left
> -        0x00, 0x00,             // int16_t bottom
> -        0x00, 0x00,             // int16_t right
> +        0x00, 0x01,             // int16_t top
> +        0x00, 0x01,             // int16_t left
> +        0x00, 0x1E,             // int16_t bottom
> +        0x00, 0xC8,             // int16_t right
>          // };
>          // StyleRecord {
>          0x00, 0x00,             // uint16_t startChar
> @@ -79,32 +92,54 @@ static av_cold int mov_text_encode_init(AVCodecContext
> *avctx)
>      if (!avctx->extradata)
>          return AVERROR(ENOMEM);
>
> +    av_bprint_init(&s->buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
> +
>      memcpy(avctx->extradata, text_sample_entry, avctx->extradata_size);
>
>      s->ass_ctx = ff_ass_split(avctx->subtitle_header);
>      return s->ass_ctx ? 0 : AVERROR_INVALIDDATA;
>  }
>
> +static void mov_text_style_cb(void *priv, const char style, int close)
> +{
> +    MovTextContext *s = priv;
> +    s->tsmb_type = MKTAG('s','t','y','l');
> +    if (!close) {
> +        s->style_start = AV_RB16(&s->text_pos);
> +        switch (style){
> +        case 'b':
> +            s->style_flag += STYLE_FLAG_BOLD;
> +            break;
> +        case 'i':
> +            s->style_flag += STYLE_FLAG_ITALIC;
> +            break;
> +        case 'u':
> +            s->style_flag += STYLE_FLAG_UNDERLINE;
> +            break;
> +        }
> +    } else {
> +        s->style_end = AV_RB16(&s->text_pos);
> +    }
> +}
> +
>  static void mov_text_text_cb(void *priv, const char *text, int len)
>  {
>      MovTextContext *s = priv;
> -    av_assert0(s->end >= s->ptr);
> -    av_strlcpy(s->ptr, text, FFMIN(s->end - s->ptr, len + 1));
> -    s->ptr += FFMIN(s->end - s->ptr, len);
> +    av_bprint_append_data(&s->buffer, text, len);
> +    s->text_pos += len;
>  }
>
>  static void mov_text_new_line_cb(void *priv, int forced)
>  {
>      MovTextContext *s = priv;
> -    av_assert0(s->end >= s->ptr);
> -    av_strlcpy(s->ptr, "\n", FFMIN(s->end - s->ptr, 2));
> -    if (s->end > s->ptr)
> -        s->ptr++;
> +    av_bprint_append_data(&s->buffer, "\n", 2);
> +    s->text_pos += 2;
>  }
>
>  static const ASSCodesCallbacks mov_text_callbacks = {
>      .text     = mov_text_text_cb,
>      .new_line = mov_text_new_line_cb,
> +    .style    = mov_text_style_cb,
>  };
>
>  static int mov_text_encode_frame(AVCodecContext *avctx, unsigned char
> *buf,
> @@ -112,10 +147,9 @@ static int mov_text_encode_frame(AVCodecContext
> *avctx, unsigned char *buf,
>  {
>      MovTextContext *s = avctx->priv_data;
>      ASSDialog *dialog;
> -    int i, len, num;
> +    int i, num;
>
> -    s->ptr = s->buffer;
> -    s->end = s->ptr + sizeof(s->buffer);
> +    av_bprint_clear(&s->buffer);
>
>      for (i = 0; i < sub->num_rects; i++) {
>
> @@ -123,33 +157,47 @@ static int mov_text_encode_frame(AVCodecContext
> *avctx, unsigned char *buf,
>              av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type
> supported.\n");
>              return AVERROR(ENOSYS);
>          }
> +        s->text_pos = 0;
>
>          dialog = ff_ass_split_dialog(s->ass_ctx, sub->rects[i]->ass, 0,
> &num);
>          for (; dialog && num--; dialog++) {
>              ff_ass_split_override_codes(&mov_text_callbacks, s,
> dialog->text);
>          }
> +        if (s->tsmb_type == MKTAG('s','t','y','l') && s->style_end) {
> +            s->tsmb_size = MKTAG(0x00, 0x00, 0x00, 0x16);
> +            s->style_entries = 0x00 | 0x01<<8;
> +            s->style_fontID = 0x00 | 0x01<<8;
> +            s->style_fontsize = 0x12;
> +            s->style_color = MKTAG(0xFF, 0xFF, 0xFF, 0xFF);
> +            av_bprint_append_data(&s->buffer, &s->tsmb_size, 4);
> +            av_bprint_append_data(&s->buffer, &s->tsmb_type, 4);
> +            av_bprint_append_data(&s->buffer, &s->style_entries, 2);
> +            av_bprint_append_data(&s->buffer, &s->style_start, 2);
> +            av_bprint_append_data(&s->buffer, &s->style_end, 2);
> +            av_bprint_append_data(&s->buffer, &s->style_fontID, 2);
> +            av_bprint_append_data(&s->buffer, &s->style_flag, 1);
> +            av_bprint_append_data(&s->buffer, &s->style_fontsize, 1);
> +            av_bprint_append_data(&s->buffer, &s->style_color, 4);
> +        }
>      }
>
> -    if (s->ptr == s->buffer)
> -        return 0;
> -
> -    AV_WB16(buf, strlen(s->buffer));
> +    AV_WB16(buf, s->text_pos);
>      buf += 2;
>
> -    len = av_strlcpy(buf, s->buffer, bufsize - 2);
> -
> -    if (len > bufsize-3) {
> -        av_log(avctx, AV_LOG_ERROR, "Buffer too small for ASS event.\n");
> -        return AVERROR(EINVAL);
> -    }
> +    if (!av_bprint_is_complete(&s->buffer))
> +        return AVERROR(ENOMEM);
> +    if (!s->buffer.len)
> +        return 0;
>
> -    return len + 2;
> +    memcpy(buf, s->buffer.str, s->buffer.len);
> +    return s->buffer.len + 2;
>  }
>
>  static int mov_text_encode_close(AVCodecContext *avctx)
>  {
>      MovTextContext *s = avctx->priv_data;
>      ff_ass_split_free(s->ass_ctx);
> +    av_bprint_finalize(&s->buffer, NULL);
>      return 0;
>  }
>
> --
> 1.9.1
>
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