PeerStreamer

/*

 * Apple HTTP Live Streaming demuxer

 * 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 demuxer

 * 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 <unistd.h>

#include "avio_internal.h"

#define INITIAL_BUFFER_SIZE 32768

/*

 * 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];

};

/*

 * Each variant has its own demuxer. If it currently is active,

 * it has an open AVIOContext too, and potentially an AVPacket

 * containing the next packet from this stream.

 */

struct variant {

    int bandwidth;

    char url[MAX_URL_SIZE];

    AVIOContext pb;

    uint8_t* read_buffer;

    URLContext *input;

    AVFormatContext *parent;

    int index;

    AVFormatContext *ctx;

    AVPacket pkt;

    int stream_offset;

    int finished;

    int target_duration;

    int start_seq_no;

    int n_segments;

    struct segment **segments;

    int needed, cur_needed;

    int cur_seq_no;

    int64_t last_load_time;

};

typedef struct AppleHTTPContext {

    int n_variants;

    struct variant **variants;

    int cur_seq_no;

    int end_of_segment;

    int first_packet;

} 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(struct variant *var)

{

    int i;

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

        av_free(var->segments[i]);

    av_freep(&var->segments);

    var->n_segments = 0;

}

static void free_variant_list(AppleHTTPContext *c)

{

    int i;

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

        struct variant *var = c->variants[i];

        free_segment_list(var);

        av_free_packet(&var->pkt);

        av_free(var->pb.buffer);

        if (var->input)

            url_close(var->input);

        if (var->ctx) {

            var->ctx->pb = NULL;

            av_close_input_file(var->ctx);

        }

        av_free(var);

    }

    av_freep(&c->variants);

    c->n_variants = 0;

}

/*

 * Used to reset a statically allocated AVPacket to a clean slate,

 * containing no data.

 */

static void reset_packet(AVPacket *pkt)

{

    av_init_packet(pkt);

    pkt->data = NULL;

}

static struct variant *new_variant(AppleHTTPContext *c, int bandwidth,

                                   const char *url, const char *base)

{

    struct variant *var = av_mallocz(sizeof(struct variant));

    if (!var)

        return NULL;

    reset_packet(&var->pkt);

    var->bandwidth = bandwidth;

    ff_make_absolute_url(var->url, sizeof(var->url), base, url);

    dynarray_add(&c->variants, &c->n_variants, var);

    return var;

}

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(AppleHTTPContext *c, const char *url,

                          struct variant *var, AVIOContext *in)

{

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

    char line[1024];

    const char *ptr;

    int close_in = 0;

    if (!in) {

        close_in = 1;

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

            return ret;

    }

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

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

        ret = AVERROR_INVALIDDATA;

        goto fail;

    }

    if (var) {

        free_segment_list(var);

        var->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)) {

            if (!var) {

                var = new_variant(c, 0, url, NULL);

                if (!var) {

                    ret = AVERROR(ENOMEM);

                    goto fail;

                }

            }

            var->target_duration = atoi(ptr);

        } else if (av_strstart(line, "#EXT-X-MEDIA-SEQUENCE:", &ptr)) {

            if (!var) {

                var = new_variant(c, 0, url, NULL);

                if (!var) {

                    ret = AVERROR(ENOMEM);

                    goto fail;

                }

            }

            var->start_seq_no = atoi(ptr);

        } else if (av_strstart(line, "#EXT-X-ENDLIST", &ptr)) {

            if (var)

                var->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_variant) {

                if (!new_variant(c, bandwidth, line, url)) {

                    ret = AVERROR(ENOMEM);

                    goto fail;

                }

                is_variant = 0;

                bandwidth  = 0;

            }

            if (is_segment) {

                struct segment *seg;

                if (!var) {

                    var = new_variant(c, 0, url, NULL);

                    if (!var) {

                        ret = AVERROR(ENOMEM);

                        goto fail;

                    }

                }

                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(&var->segments, &var->n_segments, seg);

                is_segment = 0;

            }

        }

    }

    if (var)

        var->last_load_time = av_gettime();

fail:

    if (close_in)

        avio_close(in);

    return ret;

}

static int read_data(void *opaque, uint8_t *buf, int buf_size)

{

    struct variant *v = opaque;

    AppleHTTPContext *c = v->parent->priv_data;

    int ret, i;

restart:

    if (!v->input) {

reload:

        /* If this is a live stream and target_duration has elapsed since

         * the last playlist reload, reload the variant playlists now. */

        if (!v->finished &&

            av_gettime() - v->last_load_time >= v->target_duration*1000000 &&

            (ret = parse_playlist(c, v->url, v, NULL)) < 0)

                return ret;

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

            av_log(NULL, AV_LOG_WARNING,

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

                   v->start_seq_no - v->cur_seq_no);

            v->cur_seq_no = v->start_seq_no;

        }

        if (v->cur_seq_no >= v->start_seq_no + v->n_segments) {

            if (v->finished)

                return AVERROR_EOF;

            while (av_gettime() - v->last_load_time <

                   v->target_duration*1000000) {

                if (url_interrupt_cb())

                    return AVERROR_EXIT;

                usleep(100*1000);

            }

            /* Enough time has elapsed since the last reload */

            goto reload;

        }

        ret = url_open(&v->input,

                       v->segments[v->cur_seq_no - v->start_seq_no]->url,

                       AVIO_RDONLY);

        if (ret < 0)

            return ret;

    }

    ret = url_read(v->input, buf, buf_size);

    if (ret > 0)

        return ret;

    if (ret < 0 && ret != AVERROR_EOF)

        return ret;

    url_close(v->input);

    v->input = NULL;

    v->cur_seq_no++;

    c->end_of_segment = 1;

    c->cur_seq_no = v->cur_seq_no;

    v->needed = 0;

    for (i = v->stream_offset; i < v->stream_offset + v->ctx->nb_streams; i++) {

        if (v->parent->streams[i]->discard < AVDISCARD_ALL)

            v->needed = 1;

    }

    if (!v->needed) {

        av_log(v->parent, AV_LOG_INFO, "No longer receiving variant %d\n",

               v->index);

        return AVERROR_EOF;

    }

    goto restart;

}

static int applehttp_read_header(AVFormatContext *s, AVFormatParameters *ap)

{

    AppleHTTPContext *c = s->priv_data;

    int ret = 0, i, j, stream_offset = 0;

    if ((ret = parse_playlist(c, s->filename, NULL, s->pb)) < 0)

        goto fail;

    if (c->n_variants == 0) {

        av_log(NULL, AV_LOG_WARNING, "Empty playlist\n");

        ret = AVERROR_EOF;

        goto fail;

    }

    /* If the playlist only contained variants, parse each individual

     * variant playlist. */

    if (c->n_variants > 1 || c->variants[0]->n_segments == 0) {

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

            struct variant *v = c->variants[i];

            if ((ret = parse_playlist(c, v->url, v, NULL)) < 0)

                goto fail;

        }

    }

    if (c->variants[0]->n_segments == 0) {

        av_log(NULL, AV_LOG_WARNING, "Empty playlist\n");

        ret = AVERROR_EOF;

        goto fail;

    }

    /* If this isn't a live stream, calculate the total duration of the

     * stream. */

    if (c->variants[0]->finished) {

        int64_t duration = 0;

        for (i = 0; i < c->variants[0]->n_segments; i++)

            duration += c->variants[0]->segments[i]->duration;

        s->duration = duration * AV_TIME_BASE;

    }

    /* Open the demuxer for each variant */

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

        struct variant *v = c->variants[i];

        AVInputFormat *in_fmt = NULL;

        if (v->n_segments == 0)

            continue;

        v->index  = i;

        v->needed = 1;

        v->parent = s;

        /* If this is a live stream with more than 3 segments, start at the

         * third last segment. */

        v->cur_seq_no = v->start_seq_no;

        if (!v->finished && v->n_segments > 3)

            v->cur_seq_no = v->start_seq_no + v->n_segments - 3;

        v->read_buffer = av_malloc(INITIAL_BUFFER_SIZE);

        ffio_init_context(&v->pb, v->read_buffer, INITIAL_BUFFER_SIZE, 0, v,

                          read_data, NULL, NULL);

        v->pb.seekable = 0;

        ret = av_probe_input_buffer(&v->pb, &in_fmt, v->segments[0]->url,

                                    NULL, 0, 0);

        if (ret < 0)

            goto fail;

        ret = av_open_input_stream(&v->ctx, &v->pb, v->segments[0]->url,

                                   in_fmt, NULL);

        if (ret < 0)

            goto fail;

        v->stream_offset = stream_offset;

        /* Create new AVStreams for each stream in this variant */

        for (j = 0; j < v->ctx->nb_streams; j++) {

            AVStream *st = av_new_stream(s, i);

            if (!st) {

                ret = AVERROR(ENOMEM);

                goto fail;

            }

            avcodec_copy_context(st->codec, v->ctx->streams[j]->codec);

        }

        stream_offset += v->ctx->nb_streams;

    }

    c->first_packet = 1;

    return 0;

fail:

    free_variant_list(c);

    return ret;

}

static int recheck_discard_flags(AVFormatContext *s, int first)

{

    AppleHTTPContext *c = s->priv_data;

    int i, changed = 0;

    /* Check if any new streams are needed */

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

        c->variants[i]->cur_needed = 0;;

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

        AVStream *st = s->streams[i];

        struct variant *var = c->variants[s->streams[i]->id];

        if (st->discard < AVDISCARD_ALL)

            var->cur_needed = 1;

    }

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

        struct variant *v = c->variants[i];

        if (v->cur_needed && !v->needed) {

            v->needed = 1;

            changed = 1;

            v->cur_seq_no = c->cur_seq_no;

            v->pb.eof_reached = 0;

            av_log(s, AV_LOG_INFO, "Now receiving variant %d\n", i);

        } else if (first && !v->cur_needed && v->needed) {

            if (v->input)

                url_close(v->input);

            v->input = NULL;

            v->needed = 0;

            changed = 1;

            av_log(s, AV_LOG_INFO, "No longer receiving variant %d\n", i);

        }

    }

    return changed;

}

static int applehttp_read_packet(AVFormatContext *s, AVPacket *pkt)

{

    AppleHTTPContext *c = s->priv_data;

    int ret, i, minvariant = -1;

    if (c->first_packet) {

        recheck_discard_flags(s, 1);

        c->first_packet = 0;

    }

start:

    c->end_of_segment = 0;

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

        struct variant *var = c->variants[i];

        /* Make sure we've got one buffered packet from each open variant

         * stream */

        if (var->needed && !var->pkt.data) {

            ret = av_read_frame(var->ctx, &var->pkt);

            if (ret < 0) {

                if (!var->pb.eof_reached)

                    return ret;

                reset_packet(&var->pkt);

            }

        }

        /* Check if this stream has the packet with the lowest dts */

        if (var->pkt.data) {

            if (minvariant < 0 ||

                var->pkt.dts < c->variants[minvariant]->pkt.dts)

                minvariant = i;

        }

    }

    if (c->end_of_segment) {

        if (recheck_discard_flags(s, 0))

            goto start;

    }

    /* If we got a packet, return it */

    if (minvariant >= 0) {

        *pkt = c->variants[minvariant]->pkt;

        pkt->stream_index += c->variants[minvariant]->stream_offset;

        reset_packet(&c->variants[minvariant]->pkt);

        return 0;

    }

    return AVERROR_EOF;

}

static int applehttp_close(AVFormatContext *s)

{

    AppleHTTPContext *c = s->priv_data;

    free_variant_list(c);

    return 0;

}

static int applehttp_read_seek(AVFormatContext *s, int stream_index,

                               int64_t timestamp, int flags)

{

    AppleHTTPContext *c = s->priv_data;

    int i, j, ret;

    if ((flags & AVSEEK_FLAG_BYTE) || !c->variants[0]->finished)

        return AVERROR(ENOSYS);

    timestamp = av_rescale_rnd(timestamp, 1, stream_index >= 0 ?

                               s->streams[stream_index]->time_base.den :

                               AV_TIME_BASE, flags & AVSEEK_FLAG_BACKWARD ?

                               AV_ROUND_DOWN : AV_ROUND_UP);

    ret = AVERROR(EIO);

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

        /* Reset reading */

        struct variant *var = c->variants[i];

        int64_t pos = 0;

        if (var->input) {

            url_close(var->input);

            var->input = NULL;

        }

        av_free_packet(&var->pkt);

        reset_packet(&var->pkt);

        var->pb.eof_reached = 0;

        /* Locate the segment that contains the target timestamp */

        for (j = 0; j < var->n_segments; j++) {

            if (timestamp >= pos &&

                timestamp < pos + var->segments[j]->duration) {

                var->cur_seq_no = var->start_seq_no + j;

                ret = 0;

                break;

            }

            pos += var->segments[j]->duration;

        }

    }

    return ret;

}

static int applehttp_probe(AVProbeData *p)

{

    /* Require #EXTM3U at the start, and either one of the ones below

     * somewhere for a proper match. */

    if (strncmp(p->buf, "#EXTM3U", 7))

        return 0;

    if (strstr(p->buf, "#EXT-X-STREAM-INF:")     ||

        strstr(p->buf, "#EXT-X-TARGETDURATION:") ||

        strstr(p->buf, "#EXT-X-MEDIA-SEQUENCE:"))

        return AVPROBE_SCORE_MAX;

    return 0;

}

AVInputFormat ff_applehttp_demuxer = {

    "applehttp",

    NULL_IF_CONFIG_SMALL("Apple HTTP Live Streaming format"),

    sizeof(AppleHTTPContext),

    applehttp_probe,

    applehttp_read_header,

    applehttp_read_packet,

    applehttp_close,

    applehttp_read_seek,

};