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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