FFmpeg/libavcodec/movtextenc.c

/*
 * 3GPP TS 26.245 Timed Text encoder
 * Copyright (c) 2012  Philip Langdale <philipl@overt.org>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <stdarg.h>
#include "avcodec.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/mem.h"
#include "libavutil/common.h"
#include "ass_split.h"
#include "ass.h"

#define STYLE_FLAG_BOLD         (1<<0)
#define STYLE_FLAG_ITALIC       (1<<1)
#define STYLE_FLAG_UNDERLINE    (1<<2)
#define STYLE_RECORD_SIZE       12
#define SIZE_ADD                10

#define av_bprint_append_any(buf, data, size)   av_bprint_append_data(buf, ((const char*)data), size)

typedef struct {
    uint16_t style_start;
    uint16_t style_end;
    uint8_t style_flag;
} StyleBox;

typedef struct {
    ASSSplitContext *ass_ctx;
    AVBPrint buffer;
    StyleBox **style_attributes;
    StyleBox *style_attributes_temp;
    int count;
    uint8_t style_box_flag;
    uint32_t tsmb_size;
    uint32_t tsmb_type;
    uint16_t style_entries;
    uint16_t style_fontID;
    uint8_t style_fontsize;
    uint32_t style_color;
    uint16_t text_pos;
} MovTextContext;


static av_cold int mov_text_encode_init(AVCodecContext *avctx)
{
    /*
     * For now, we'll use a fixed default style. When we add styling
     * support, this will be generated from the ASS style.
     */
    static const uint8_t text_sample_entry[] = {
        0x00, 0x00, 0x00, 0x00, // uint32_t displayFlags
        0x01,                   // int8_t horizontal-justification
        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
        // };
        // StyleRecord {
        0x00, 0x00,             // uint16_t startChar
        0x00, 0x00,             // uint16_t endChar
        0x00, 0x01,             // uint16_t font-ID
        0x00,                   // uint8_t face-style-flags
        0x12,                   // uint8_t font-size
        0xFF, 0xFF, 0xFF, 0xFF, // uint8_t text-color-rgba[4]
        // };
        // FontTableBox {
        0x00, 0x00, 0x00, 0x12, // uint32_t size
        'f', 't', 'a', 'b',     // uint8_t name[4]
        0x00, 0x01,             // uint16_t entry-count
        // FontRecord {
        0x00, 0x01,             // uint16_t font-ID
        0x05,                   // uint8_t font-name-length
        'S', 'e', 'r', 'i', 'f',// uint8_t font[font-name-length]
        // };
        // };
    };

    MovTextContext *s = avctx->priv_data;

    avctx->extradata_size = sizeof text_sample_entry;
    avctx->extradata = av_mallocz(avctx->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);
    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;
    if (!close) {
        if (s->style_box_flag == 0) {   //first style entry

            s->style_attributes_temp = av_malloc(sizeof(*s->style_attributes_temp));

            if (!s->style_attributes_temp) {
                av_bprint_clear(&s->buffer);
                s->style_box_flag = 0;
                return;
            }

            s->style_attributes_temp->style_flag = 0;
            s->style_attributes_temp->style_start = AV_RB16(&s->text_pos);
        } else {
            if (s->style_attributes_temp->style_flag) { //break the style record here and start a new one
                s->style_attributes_temp->style_end = AV_RB16(&s->text_pos);
                av_dynarray_add(&s->style_attributes, &s->count, s->style_attributes_temp);

                s->style_attributes_temp = av_malloc(sizeof(*s->style_attributes_temp));

                if (!s->style_attributes_temp) {
                    av_bprint_clear(&s->buffer);
                    s->style_box_flag = 0;
                    return;
                }

                s->style_attributes_temp->style_flag = s->style_attributes[s->count - 1]->style_flag;
                s->style_attributes_temp->style_start = AV_RB16(&s->text_pos);
            } else {
                s->style_attributes_temp->style_flag = 0;
                s->style_attributes_temp->style_start = AV_RB16(&s->text_pos);
            }
        }
        switch (style){
        case 'b':
            s->style_attributes_temp->style_flag |= STYLE_FLAG_BOLD;
            break;
        case 'i':
            s->style_attributes_temp->style_flag |= STYLE_FLAG_ITALIC;
            break;
        case 'u':
            s->style_attributes_temp->style_flag |= STYLE_FLAG_UNDERLINE;
            break;
        }
    } else {
        s->style_attributes_temp->style_end = AV_RB16(&s->text_pos);
        av_dynarray_add(&s->style_attributes, &s->count, s->style_attributes_temp);

        s->style_attributes_temp = av_malloc(sizeof(*s->style_attributes_temp));

        if (!s->style_attributes_temp) {
            av_bprint_clear(&s->buffer);
            s->style_box_flag = 0;
            return;
        }

        s->style_attributes_temp->style_flag = s->style_attributes[s->count - 1]->style_flag;
        switch (style){
        case 'b':
            s->style_attributes_temp->style_flag &= ~STYLE_FLAG_BOLD;
            break;
        case 'i':
            s->style_attributes_temp->style_flag &= ~STYLE_FLAG_ITALIC;
            break;
        case 'u':
            s->style_attributes_temp->style_flag &= ~STYLE_FLAG_UNDERLINE;
            break;
        }
        if (s->style_attributes_temp->style_flag) { //start of new style record
            s->style_attributes_temp->style_start = AV_RB16(&s->text_pos);
        }
    }
    s->style_box_flag = 1;
}

static void mov_text_text_cb(void *priv, const char *text, int len)
{
    MovTextContext *s = priv;
    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_bprint_append_data(&s->buffer, "\n", 1);
    s->text_pos += 1;
}

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,
                                 int bufsize, const AVSubtitle *sub)
{
    MovTextContext *s = avctx->priv_data;
    ASSDialog *dialog;
    int i, j, num, length;

    s->text_pos = 0;
    s->count = 0;
    s->style_box_flag = 0;
    s->style_entries = 0;

    for (i = 0; i < sub->num_rects; i++) {

        if (sub->rects[i]->type != SUBTITLE_ASS) {
            av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type supported.\n");
            return AVERROR(ENOSYS);
        }

        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->style_box_flag) {
            s->tsmb_size = s->count * STYLE_RECORD_SIZE + SIZE_ADD;  //size of one style record is 12 bytes
            s->tsmb_size = AV_RB32(&s->tsmb_size);
            s->tsmb_type = MKTAG('s','t','y','l');
            s->style_entries = AV_RB16(&s->count);
            s->style_fontID = 0x00 | 0x01<<8;
            s->style_fontsize = 0x12;
            s->style_color = MKTAG(0xFF, 0xFF, 0xFF, 0xFF);
            /*The above three attributes are hard coded for now
            but will come from ASS style in the future*/
            av_bprint_append_any(&s->buffer, &s->tsmb_size, 4);
            av_bprint_append_any(&s->buffer, &s->tsmb_type, 4);
            av_bprint_append_any(&s->buffer, &s->style_entries, 2);
            for (j = 0; j < s->count; j++) {
                av_bprint_append_any(&s->buffer, &s->style_attributes[j]->style_start, 2);
                av_bprint_append_any(&s->buffer, &s->style_attributes[j]->style_end, 2);
                av_bprint_append_any(&s->buffer, &s->style_fontID, 2);
                av_bprint_append_any(&s->buffer, &s->style_attributes[j]->style_flag, 1);
                av_bprint_append_any(&s->buffer, &s->style_fontsize, 1);
                av_bprint_append_any(&s->buffer, &s->style_color, 4);
            }
            for (j = 0; j < s->count; j++) {
                av_freep(&s->style_attributes[j]);
            }
            av_freep(&s->style_attributes);
            av_freep(&s->style_attributes_temp);
        }
    }

    AV_WB16(buf, s->text_pos);
    buf += 2;

    if (!av_bprint_is_complete(&s->buffer)) {
        length = AVERROR(ENOMEM);
        goto exit;
    }

    if (!s->buffer.len) {
        length = 0;
        goto exit;
    }

    if (s->buffer.len > bufsize - 3) {
        av_log(avctx, AV_LOG_ERROR, "Buffer too small for ASS event.\n");
        length = AVERROR(EINVAL);
        goto exit;
    }

    memcpy(buf, s->buffer.str, s->buffer.len);
    length = s->buffer.len + 2;

exit:
    av_bprint_clear(&s->buffer);
    return length;
}

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;
}

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),
    .init           = mov_text_encode_init,
    .encode_sub     = mov_text_encode_frame,
    .close          = mov_text_encode_close,
};