FFmpeg4/libavformat/lrcenc.c

/*
 * LRC lyrics file format decoder
 * Copyright (c) 2014 StarBrilliant <m13253@hotmail.com>
 *
 * 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 <inttypes.h>
#include <stdint.h>
#include <string.h>

#include "avformat.h"
#include "internal.h"
#include "lrc.h"
#include "metadata.h"
#include "subtitles.h"
#include "version.h"
#include "libavutil/bprint.h"
#include "libavutil/dict.h"
#include "libavutil/log.h"
#include "libavutil/macros.h"

static int lrc_write_header(AVFormatContext *s)
{
    const AVDictionaryEntry *metadata_item;

    if(s->nb_streams != 1 ||
       s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE) {
        av_log(s, AV_LOG_ERROR,
               "LRC supports only a single subtitle stream.\n");
        return AVERROR(EINVAL);
    }
    if(s->streams[0]->codecpar->codec_id != AV_CODEC_ID_SUBRIP &&
       s->streams[0]->codecpar->codec_id != AV_CODEC_ID_TEXT) {
        av_log(s, AV_LOG_ERROR, "Unsupported subtitle codec: %s\n",
               avcodec_get_name(s->streams[0]->codecpar->codec_id));
        return AVERROR(EINVAL);
    }
    avpriv_set_pts_info(s->streams[0], 64, 1, 100);

    ff_standardize_creation_time(s);
    ff_metadata_conv_ctx(s, ff_lrc_metadata_conv, NULL);
    if(!(s->flags & AVFMT_FLAG_BITEXACT)) { // avoid breaking regression tests
        /* LRC provides a metadata slot for specifying encoder version
         * in addition to encoder name. We will store LIBAVFORMAT_VERSION
         * to it.
         */
        av_dict_set(&s->metadata, "ve", AV_STRINGIFY(LIBAVFORMAT_VERSION), 0);
    } else {
        av_dict_set(&s->metadata, "ve", NULL, 0);
    }
    for(metadata_item = NULL;
       (metadata_item = av_dict_get(s->metadata, "", metadata_item,
                                    AV_DICT_IGNORE_SUFFIX));) {
        char *delim;
        if(!metadata_item->value[0]) {
            continue;
        }
        while((delim = strchr(metadata_item->value, '\n'))) {
            *delim = ' ';
        }
        while((delim = strchr(metadata_item->value, '\r'))) {
            *delim = ' ';
        }
        avio_printf(s->pb, "[%s:%s]\n",
                    metadata_item->key, metadata_item->value);
    }
    avio_printf(s->pb, "\n");
    return 0;
}

static int lrc_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    if(pkt->pts != AV_NOPTS_VALUE) {
        char *data = av_malloc(pkt->size + 1);
        char *line;
        char *delim;

        if(!data) {
            return AVERROR(ENOMEM);
        }
        memcpy(data, pkt->data, pkt->size);
        data[pkt->size] = '\0';

        for(delim = data + pkt->size - 1;
            delim >= data && (delim[0] == '\n' || delim[0] == '\r'); delim--) {
            delim[0] = '\0'; // Strip last empty lines
        }
        line = data;
        while(line[0] == '\n' || line[0] == '\r') {
            line++; // Skip first empty lines
        }

        while(line) {
            delim = strchr(line, '\n');
            if(delim) {
                if(delim > line && delim[-1] == '\r') {
                    delim[-1] = '\0';
                }
                delim[0] = '\0';
                delim++;
            }
            if(line[0] == '[') {
                av_log(s, AV_LOG_WARNING,
                       "Subtitle starts with '[', may cause problems with LRC format.\n");
            }

            if(pkt->pts >= 0) {
                avio_printf(s->pb, "[%02"PRId64":%02"PRId64".%02"PRId64"]",
                            (pkt->pts / 6000),
                            ((pkt->pts / 100) % 60),
                            (pkt->pts % 100));
            } else {
                /* Offset feature of LRC can easily make pts negative,
                 * we just output it directly and let the player drop it. */
                avio_printf(s->pb, "[-%02"PRId64":%02"PRId64".%02"PRId64"]",
                            (-pkt->pts) / 6000,
                            ((-pkt->pts) / 100) % 60,
                            (-pkt->pts) % 100);
            }
            avio_printf(s->pb, "%s\n", line);
            line = delim;
        }
        av_free(data);
    }
    return 0;
}

AVOutputFormat ff_lrc_muxer = {
    .name           = "lrc",
    .long_name      = NULL_IF_CONFIG_SMALL("LRC lyrics"),
    .extensions     = "lrc",
    .priv_data_size = 0,
    .write_header   = lrc_write_header,
    .write_packet   = lrc_write_packet,
    .flags          = AVFMT_VARIABLE_FPS | AVFMT_GLOBALHEADER |
                      AVFMT_TS_NEGATIVE | AVFMT_TS_NONSTRICT,
    .subtitle_codec = AV_CODEC_ID_SUBRIP
};