FFmpeg总结（十四）FFmpeg如何解析直播点播m3u8

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看下直播m3u8结构：

#EXTM3U#EXT-X-MEDIA-SEQUENCE:3918#EXT-X-TARGETDURATION:10#EXTINF:10,2017071806/1500358480.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358490.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358500.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358510.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358520.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358535.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358545.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358555.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358565.ts?type=hls_live_slice#EXTINF:10,2017071806/1500358575.ts?type=hls_live_slice

看下点播m3u8结构：

#EXTM3U#EXT-X-VERSION:3#EXT-X-MEDIA-SEQUENCE:0#EXT-X-TARGETDURATION:19#EXT-X-PLAYLIST-TYPE:VOD#EXTINF:9.800,00_d0024036a7j.320086.1.ts?index=0&start=0&end=9800&brs=0&bre=1509827&ver=4#EXTINF:10.480,01_d0024036a7j.320086.1.ts?index=1&start=9800&end=20280&brs=1509828&bre=3828055&ver=4#EXTINF:9.960,02_d0024036a7j.320086.1.ts?index=2&start=20280&end=30240&brs=3828056&bre=6248743&ver=4#EXTINF:9.520,03_d0024036a7j.320086.1.ts?index=3&start=30240&end=39760&brs=6248744&bre=8234399&ver=4#EXTINF:9.920,04_d0024036a7j.320086.1.ts?index=4&start=39760&end=49680&brs=8234400&bre=10619931&ver=4#EXTINF:9.960,05_d0024036a7j.320086.1.ts?index=5&start=49680&end=59640&brs=10619932&bre=13400639&ver=4#EXTINF:9.720,06_d0024036a7j.320086.1.ts?index=6&start=59640&end=69360&brs=13400640&bre=16777683&ver=4#EXTINF:10.880,07_d0024036a7j.320086.1.ts?index=7&start=69360&end=80240&brs=16777684&bre=19713867&ver=4...省略#EXTINF:9.960,029_d0024036a7j.320086.2.ts?index=29&start=295520&end=305480&brs=0&bre=1287611&ver=4#EXTINF:9.040,...省略#EXTINF:7.240,0315_d0024036a7j.320086.11.ts?index=315&start=3181360&end=3188600&brs=30080752&bre=31204615&ver=4#EXT-X-ENDLIST

区别：

• 1、 每个TS分片时间，通过标签EXTINF，后面有的是float型，有的是int型，一般为10s（也有不会10s的），最后如果没有10s，就取对应时间。

• 2、不是所有点播m3u8中都有EXT-X-PLAYLIST-TYPE，表明类型。最直接区分就是直播m3u8没有EXT-X-ENDLIST标签，因为是实时流，自然不会有结束，否则就是点播流了。

FFmpeg是如何解析直播，点播的HLS？在\libavformat\hlsproto.c中，就是实现步骤，先打开m3u8文件，然后parse。

static int hls_open(URLContext *h, const char *uri, int flags){    HLSContext *s = h->priv_data;    int ret, i;    const char *nested_url;    if (flags & AVIO_FLAG_WRITE)        return AVERROR(ENOSYS);    h->is_streamed = 1;    if (av_strstart(uri, "hls+", &nested_url)) {        av_strlcpy(s->playlisturl, nested_url, sizeof(s->playlisturl));    } else if (av_strstart(uri, "hls://", &nested_url)) {        av_log(h, AV_LOG_ERROR,               "No nested protocol specified. Specify e.g. hls+http://%s\n",               nested_url);        ret = AVERROR(EINVAL);        goto fail;    } else {        av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);        ret = AVERROR(EINVAL);        goto fail;    }    av_log(h, AV_LOG_WARNING,           "Using the hls protocol is discouraged, please try using the "           "hls demuxer instead. The hls demuxer should be more complete "           "and work as well as the protocol implementation. (If not, "           "please report it.) To use the demuxer, simply use %s as url.\n",           s->playlisturl);    if ((ret = parse_playlist(h, s->playlisturl)) < 0)        goto fail;    if (s->n_segments == 0 && s->n_variants > 0) {        int max_bandwidth = 0, maxvar = -1;        for (i = 0; i < s->n_variants; i++) {            if (s->variants[i]->bandwidth > max_bandwidth || i == 0) {                max_bandwidth = s->variants[i]->bandwidth;                maxvar = i;            }        }        av_strlcpy(s->playlisturl, s->variants[maxvar]->url,                   sizeof(s->playlisturl));        if ((ret = parse_playlist(h, s->playlisturl)) < 0)            goto fail;    }    if (s->n_segments == 0) {        av_log(h, AV_LOG_WARNING, "Empty playlist\n");        ret = AVERROR(EIO);        goto fail;    }    s->cur_seq_no = s->start_seq_no;    if (!s->finished && s->n_segments >= 3)        s->cur_seq_no = s->start_seq_no + s->n_segments - 3;    return 0;fail:    hls_close(h);    return ret;}

解析playlist中的ts流

static int parse_playlist(URLContext *h, const char *url){    HLSContext *s = h->priv_data;    AVIOContext *in;    int ret = 0, is_segment = 0, is_variant = 0, bandwidth = 0;    int64_t duration = 0;    char line[1024];    const char *ptr;    if ((ret = ffio_open_whitelist(&in, url, AVIO_FLAG_READ,                                   &h->interrupt_callback, NULL,                                   h->protocol_whitelist, h->protocol_blacklist)) < 0)        return ret;    read_chomp_line(in, line, sizeof(line));    if (strcmp(line, "#EXTM3U")) {        ret = AVERROR_INVALIDDATA;        goto fail;    }    free_segment_list(s);    s->finished = 0;    while (!avio_feof(in)) {        read_chomp_line(in, line, sizeof(line));        if (av_strstart(line, "#EXT-X-STREAM-INF:", &ptr)) {            struct variant_info info = {{0}};            is_variant = 1;            ff_parse_key_value(ptr, (ff_parse_key_val_cb) handle_variant_args,                               &info);            bandwidth = atoi(info.bandwidth);        } else if (av_strstart(line, "#EXT-X-TARGETDURATION:", &ptr)) {            s->target_duration = atoi(ptr) * AV_TIME_BASE;        } else if (av_strstart(line, "#EXT-X-MEDIA-SEQUENCE:", &ptr)) {            s->start_seq_no = atoi(ptr);        } else if (av_strstart(line, "#EXT-X-ENDLIST", &ptr)) {            s->finished = 1;        } else if (av_strstart(line, "#EXTINF:", &ptr)) {            is_segment = 1;            duration = atof(ptr) * AV_TIME_BASE;        } else if (av_strstart(line, "#", NULL)) {            continue;        } else if (line[0]) {            if (is_segment) {                struct segment *seg = av_malloc(sizeof(struct segment));                if (!seg) {                    ret = AVERROR(ENOMEM);                    goto fail;                }                seg->duration = duration;                ff_make_absolute_url(seg->url, sizeof(seg->url), url, line);                dynarray_add(&s->segments, &s->n_segments, seg);                is_segment = 0;            } else if (is_variant) {                struct variant *var = av_malloc(sizeof(struct variant));                if (!var) {                    ret = AVERROR(ENOMEM);                    goto fail;                }                var->bandwidth = bandwidth;                ff_make_absolute_url(var->url, sizeof(var->url), url, line);                dynarray_add(&s->variants, &s->n_variants, var);                is_variant = 0;            }        }    }    s->last_load_time = av_gettime_relative();fail:    avio_close(in);    return ret;}

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