PeerStreamer

/*

 * Apple HTTP Live Streaming Protocol Handler

 * Copyright (c) 2010 Martin Storsjo

 *

 * This file is part of Libav.

 *

 * Libav 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.

 *

 * Libav 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 Libav; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * Apple HTTP Live Streaming Protocol Handler

 * http://tools.ietf.org/html/draft-pantos-http-live-streaming

 */

#define _XOPEN_SOURCE 600

#include "libavutil/avstring.h"

#include "avformat.h"

#include "internal.h"

#include "url.h"

#include <unistd.h>

/*

 * An apple http stream consists of a playlist with media segment files,

 * played sequentially. There may be several playlists with the same

 * video content, in different bandwidth variants, that are played in

 * parallel (preferrably only one bandwidth variant at a time). In this case,

 * the user supplied the url to a main playlist that only lists the variant

 * playlists.

 *

 * If the main playlist doesn't point at any variants, we still create

 * one anonymous toplevel variant for this, to maintain the structure.

 */

struct segment {

    int duration;

    char url[MAX_URL_SIZE];

};

struct variant {

    int bandwidth;

    char url[MAX_URL_SIZE];

};

typedef struct AppleHTTPContext {

    char playlisturl[MAX_URL_SIZE];

    int target_duration;

    int start_seq_no;

    int finished;

    int n_segments;

    struct segment **segments;

    int n_variants;

    struct variant **variants;

    int cur_seq_no;

    URLContext *seg_hd;

    int64_t last_load_time;

} AppleHTTPContext;

static int read_chomp_line(AVIOContext *s, char *buf, int maxlen)

{

    int len = ff_get_line(s, buf, maxlen);

    while (len > 0 && isspace(buf[len - 1]))

        buf[--len] = '\0';

    return len;

}

static void free_segment_list(AppleHTTPContext *s)

{

    int i;

    for (i = 0; i < s->n_segments; i++)

        av_free(s->segments[i]);

    av_freep(&s->segments);

    s->n_segments = 0;

}

static void free_variant_list(AppleHTTPContext *s)

{

    int i;

    for (i = 0; i < s->n_variants; i++)

        av_free(s->variants[i]);

    av_freep(&s->variants);

    s->n_variants = 0;

}

struct variant_info {

    char bandwidth[20];

};

static void handle_variant_args(struct variant_info *info, const char *key,

                                int key_len, char **dest, int *dest_len)

{

    if (!strncmp(key, "BANDWIDTH=", key_len)) {

        *dest     =        info->bandwidth;

        *dest_len = sizeof(info->bandwidth);

    }

}

static int parse_playlist(URLContext *h, const char *url)

{

    AppleHTTPContext *s = h->priv_data;

    AVIOContext *in;

    int ret = 0, duration = 0, is_segment = 0, is_variant = 0, bandwidth = 0;

    char line[1024];

    const char *ptr;

    if ((ret = avio_open(&in, url, AVIO_FLAG_READ)) < 0)

        return ret;

    read_chomp_line(in, line, sizeof(line));

    if (strcmp(line, "#EXTM3U"))

        return AVERROR_INVALIDDATA;

    free_segment_list(s);

    s->finished = 0;

    while (!in->eof_reached) {

        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);

        } 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 = atoi(ptr);

        } 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();

fail:

    avio_close(in);

    return ret;

}

static int applehttp_open(URLContext *h, const char *uri, int flags)

{

    AppleHTTPContext *s;

    int ret, i;

    const char *nested_url;

    if (flags & AVIO_FLAG_WRITE)

        return AVERROR(ENOSYS);

    s = av_mallocz(sizeof(AppleHTTPContext));

    if (!s)

        return AVERROR(ENOMEM);

    h->priv_data = s;

    h->is_streamed = 1;

    if (av_strstart(uri, "applehttp+", &nested_url)) {

        av_strlcpy(s->playlisturl, nested_url, sizeof(s->playlisturl));

    } else if (av_strstart(uri, "applehttp://", &nested_url)) {

        av_strlcpy(s->playlisturl, "http://", sizeof(s->playlisturl));

        av_strlcat(s->playlisturl, nested_url, sizeof(s->playlisturl));

    } else {

        av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);

        ret = AVERROR(EINVAL);

        goto fail;

    }

    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:

    av_free(s);

    return ret;

}

static int applehttp_read(URLContext *h, uint8_t *buf, int size)

{

    AppleHTTPContext *s = h->priv_data;

    const char *url;

    int ret;

start:

    if (s->seg_hd) {

        ret = ffurl_read(s->seg_hd, buf, size);

        if (ret > 0)

            return ret;

    }

    if (s->seg_hd) {

        ffurl_close(s->seg_hd);

        s->seg_hd = NULL;

        s->cur_seq_no++;

    }

retry:

    if (!s->finished) {

        int64_t now = av_gettime();

        if (now - s->last_load_time >= s->target_duration*1000000)

            if ((ret = parse_playlist(h, s->playlisturl)) < 0)

                return ret;

    }

    if (s->cur_seq_no < s->start_seq_no) {

        av_log(h, AV_LOG_WARNING,

               "skipping %d segments ahead, expired from playlist\n",

               s->start_seq_no - s->cur_seq_no);

        s->cur_seq_no = s->start_seq_no;

    }

    if (s->cur_seq_no - s->start_seq_no >= s->n_segments) {

        if (s->finished)

            return AVERROR_EOF;

        while (av_gettime() - s->last_load_time < s->target_duration*1000000) {

            if (url_interrupt_cb())

                return AVERROR_EXIT;

            usleep(100*1000);

        }

        goto retry;

    }

    url = s->segments[s->cur_seq_no - s->start_seq_no]->url,

    av_log(h, AV_LOG_DEBUG, "opening %s\n", url);

    ret = ffurl_open(&s->seg_hd, url, AVIO_FLAG_READ);

    if (ret < 0) {

        if (url_interrupt_cb())

            return AVERROR_EXIT;

        av_log(h, AV_LOG_WARNING, "Unable to open %s\n", url);

        s->cur_seq_no++;

        goto retry;

    }

    goto start;

}

static int applehttp_close(URLContext *h)

{

    AppleHTTPContext *s = h->priv_data;

    free_segment_list(s);

    free_variant_list(s);

    ffurl_close(s->seg_hd);

    av_free(s);

    return 0;

}

URLProtocol ff_applehttp_protocol = {

    .name      = "applehttp",

    .url_open  = applehttp_open,

    .url_read  = applehttp_read,

    .url_close = applehttp_close,

    .flags     = URL_PROTOCOL_FLAG_NESTED_SCHEME,

};