ffserver.c

/*
 * Multiple format streaming server
 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
 *
 * This library 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 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#define HAVE_AV_CONFIG_H
#include "avformat.h"

#include <stdarg.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/poll.h>
#include <errno.h>
#include <sys/time.h>
#include <time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <ctype.h>
#include <signal.h>
#ifdef CONFIG_HAVE_DLFCN
#include <dlfcn.h>
#endif

#include "ffserver.h"

/* maximum number of simultaneous HTTP connections */
#define HTTP_MAX_CONNECTIONS 2000

enum HTTPState {
    HTTPSTATE_WAIT_REQUEST,
    HTTPSTATE_SEND_HEADER,
    HTTPSTATE_SEND_DATA_HEADER,
    HTTPSTATE_SEND_DATA,          /* sending TCP or UDP data */
    HTTPSTATE_SEND_DATA_TRAILER,
    HTTPSTATE_RECEIVE_DATA,       
    HTTPSTATE_WAIT_FEED,          /* wait for data from the feed */
    HTTPSTATE_WAIT,               /* wait before sending next packets */
    HTTPSTATE_WAIT_SHORT,         /* short wait for short term 
                                     bandwidth limitation */
    HTTPSTATE_READY,

    RTSPSTATE_WAIT_REQUEST,
    RTSPSTATE_SEND_REPLY,
};

const char *http_state[] = {
    "HTTP_WAIT_REQUEST",
    "HTTP_SEND_HEADER",

    "SEND_DATA_HEADER",
    "SEND_DATA",
    "SEND_DATA_TRAILER",
    "RECEIVE_DATA",
    "WAIT_FEED",
    "WAIT",
    "WAIT_SHORT",
    "READY",

    "RTSP_WAIT_REQUEST",
    "RTSP_SEND_REPLY",
};

#define IOBUFFER_INIT_SIZE 8192

/* coef for exponential mean for bitrate estimation in statistics */
#define AVG_COEF 0.9

/* timeouts are in ms */
#define HTTP_REQUEST_TIMEOUT (15 * 1000)
#define RTSP_REQUEST_TIMEOUT (3600 * 24 * 1000)

#define SYNC_TIMEOUT (10 * 1000)

typedef struct {
    INT64 count1, count2;
    long time1, time2;
} DataRateData;

/* context associated with one connection */
typedef struct HTTPContext {
    enum HTTPState state;
    int fd; /* socket file descriptor */
    struct sockaddr_in from_addr; /* origin */
    struct pollfd *poll_entry; /* used when polling */
    long timeout;
    UINT8 *buffer_ptr, *buffer_end;
    int http_error;
    struct HTTPContext *next;
    int got_key_frame; /* stream 0 => 1, stream 1 => 2, stream 2=> 4 */
    INT64 data_count;
    /* feed input */
    int feed_fd;
    /* input format handling */
    AVFormatContext *fmt_in;
    long start_time;            /* In milliseconds - this wraps fairly often */
    INT64 first_pts;            /* initial pts value */
    int pts_stream_index;       /* stream we choose as clock reference */
    /* output format handling */
    struct FFStream *stream;
    /* -1 is invalid stream */
    int feed_streams[MAX_STREAMS]; /* index of streams in the feed */
    int switch_feed_streams[MAX_STREAMS]; /* index of streams in the feed */
    int switch_pending;
    AVFormatContext fmt_ctx; /* instance of FFStream for one user */
    int last_packet_sent; /* true if last data packet was sent */
    int suppress_log;
    DataRateData datarate;
    int wmp_client_id;
    char protocol[16];
    char method[16];
    char url[128];
    int buffer_size;
    UINT8 *buffer;
    int is_packetized; /* if true, the stream is packetized */
    int packet_stream_index; /* current stream for output in state machine */
    
    /* RTSP state specific */
    UINT8 *pb_buffer; /* XXX: use that in all the code */
    ByteIOContext *pb;
    int seq; /* RTSP sequence number */

    /* RTP state specific */
    enum RTSPProtocol rtp_protocol;
    char session_id[32]; /* session id */
    AVFormatContext *rtp_ctx[MAX_STREAMS];
    URLContext *rtp_handles[MAX_STREAMS];
    /* RTP short term bandwidth limitation */
    int packet_byte_count;
    int packet_start_time_us; /* used for short durations (a few
                                 seconds max) */
} HTTPContext;

static AVFrame dummy_frame;

/* each generated stream is described here */
enum StreamType {
    STREAM_TYPE_LIVE,
    STREAM_TYPE_STATUS,
    STREAM_TYPE_REDIRECT,
};

enum IPAddressAction {
    IP_ALLOW = 1,
    IP_DENY,
};

typedef struct IPAddressACL {
    struct IPAddressACL *next;
    enum IPAddressAction action;
    struct in_addr first;
    struct in_addr last;
} IPAddressACL;

/* description of each stream of the ffserver.conf file */
typedef struct FFStream {
    enum StreamType stream_type;
    char filename[1024];     /* stream filename */
    struct FFStream *feed;   /* feed we are using (can be null if
                                coming from file) */
    AVOutputFormat *fmt;
    IPAddressACL *acl;
    int nb_streams;
    int prebuffer;      /* Number of millseconds early to start */
    long max_time;      /* Number of milliseconds to run */
    int send_on_key;
    AVStream *streams[MAX_STREAMS];
    int feed_streams[MAX_STREAMS]; /* index of streams in the feed */
    char feed_filename[1024]; /* file name of the feed storage, or
                                 input file name for a stream */
    char author[512];
    char title[512];
    char copyright[512];
    char comment[512];
    pid_t pid;  /* Of ffmpeg process */
    time_t pid_start;  /* Of ffmpeg process */
    char **child_argv;
    struct FFStream *next;
    int bandwidth; /* bandwidth, in kbits/s */
    /* RTSP options */
    char *rtsp_option;
    /* multicast specific */
    int is_multicast;
    struct in_addr multicast_ip;
    int multicast_port; /* first port used for multicast */
    int multicast_ttl;
    int loop; /* if true, send the stream in loops (only meaningful if file) */

    /* feed specific */
    int feed_opened;     /* true if someone is writing to the feed */
    int is_feed;         /* true if it is a feed */
    int conns_served;
    INT64 bytes_served;
    INT64 feed_max_size;      /* maximum storage size */
    INT64 feed_write_index;   /* current write position in feed (it wraps round) */
    INT64 feed_size;          /* current size of feed */
    struct FFStream *next_feed;
} FFStream;

typedef struct FeedData {
    long long data_count;
    float avg_frame_size;   /* frame size averraged over last frames with exponential mean */
} FeedData;

struct sockaddr_in my_http_addr;
struct sockaddr_in my_rtsp_addr;

char logfilename[1024];
HTTPContext *first_http_ctx;
FFStream *first_feed;   /* contains only feeds */
FFStream *first_stream; /* contains all streams, including feeds */

static void new_connection(int server_fd, int is_rtsp);
static void close_connection(HTTPContext *c);

/* HTTP handling */
static int handle_connection(HTTPContext *c);
static int http_parse_request(HTTPContext *c);
static int http_send_data(HTTPContext *c);
static void compute_stats(HTTPContext *c);
static int open_input_stream(HTTPContext *c, const char *info);
static int http_start_receive_data(HTTPContext *c);
static int http_receive_data(HTTPContext *c);
static int compute_send_delay(HTTPContext *c);

/* RTSP handling */
static int rtsp_parse_request(HTTPContext *c);
static void rtsp_cmd_describe(HTTPContext *c, const char *url);
static void rtsp_cmd_setup(HTTPContext *c, const char *url, RTSPHeader *h);
static void rtsp_cmd_play(HTTPContext *c, const char *url, RTSPHeader *h);
static void rtsp_cmd_pause(HTTPContext *c, const char *url, RTSPHeader *h);
static void rtsp_cmd_teardown(HTTPContext *c, const char *url, RTSPHeader *h);

/* SDP handling */
static int prepare_sdp_description(FFStream *stream, UINT8 **pbuffer, 
                                   struct in_addr my_ip);

/* RTP handling */
static HTTPContext *rtp_new_connection(struct sockaddr_in *from_addr, 
                                       FFStream *stream, const char *session_id);
static int rtp_new_av_stream(HTTPContext *c, 
                             int stream_index, struct sockaddr_in *dest_addr);

static const char *my_program_name;
static const char *my_program_dir;

static int ffserver_debug;
static int ffserver_daemon;
static int no_launch;
static int need_to_start_children;

int nb_max_connections;
int nb_connections;

int max_bandwidth;
int current_bandwidth;

static long cur_time;           // Making this global saves on passing it around everywhere

static long gettime_ms(void)
{
    struct timeval tv;

    gettimeofday(&tv,NULL);
    return (long long)tv.tv_sec * 1000 + (tv.tv_usec / 1000);
}

static FILE *logfile = NULL;

static void http_log(const char *fmt, ...)
{
    va_list ap;
    va_start(ap, fmt);
    
    if (logfile) {
        vfprintf(logfile, fmt, ap);
        fflush(logfile);
    }
    va_end(ap);
}

static char *ctime1(char *buf2)
{
    time_t ti;
    char *p;

    ti = time(NULL);
    p = ctime(&ti);
    strcpy(buf2, p);
    p = buf2 + strlen(p) - 1;
    if (*p == '\n')
        *p = '\0';
    return buf2;
}

static void log_connection(HTTPContext *c)
{
    char buf2[32];

    if (c->suppress_log) 
        return;

    http_log("%s - - [%s] \"%s %s %s\" %d %lld\n", 
             inet_ntoa(c->from_addr.sin_addr), 
             ctime1(buf2), c->method, c->url, 
             c->protocol, (c->http_error ? c->http_error : 200), c->data_count);
}

static void update_datarate(DataRateData *drd, INT64 count)
{
    if (!drd->time1 && !drd->count1) {
        drd->time1 = drd->time2 = cur_time;
        drd->count1 = drd->count2 = count;
    } else {
        if (cur_time - drd->time2 > 5000) {
            drd->time1 = drd->time2;
            drd->count1 = drd->count2;
            drd->time2 = cur_time;
            drd->count2 = count;
        }
    }
}

/* In bytes per second */
static int compute_datarate(DataRateData *drd, INT64 count)
{
    if (cur_time == drd->time1)
        return 0;
    
    return ((count - drd->count1) * 1000) / (cur_time - drd->time1);
}

static int get_longterm_datarate(DataRateData *drd, INT64 count)
{
    /* You get the first 3 seconds flat out */
    if (cur_time - drd->time1 < 3000)
        return 0;
    return compute_datarate(drd, count);
}


static void start_children(FFStream *feed)
{
    if (no_launch)
        return;

    for (; feed; feed = feed->next) {
        if (feed->child_argv && !feed->pid) {
            feed->pid_start = time(0);

            feed->pid = fork();

            if (feed->pid < 0) {
                fprintf(stderr, "Unable to create children\n");
                exit(1);
            }
            if (!feed->pid) {
                /* In child */
                char pathname[1024];
                char *slash;
                int i;

                for (i = 3; i < 256; i++) {
                    close(i);
                }

                if (!ffserver_debug) {
                    i = open("/dev/null", O_RDWR);
                    if (i)
                        dup2(i, 0);
                    dup2(i, 1);
                    dup2(i, 2);
                    if (i)
                        close(i);
                }

                pstrcpy(pathname, sizeof(pathname), my_program_name);

                slash = strrchr(pathname, '/');
                if (!slash) {
                    slash = pathname;
                } else {
                    slash++;
                }
                strcpy(slash, "ffmpeg");

                /* This is needed to make relative pathnames work */
                chdir(my_program_dir);

                signal(SIGPIPE, SIG_DFL);

                execvp(pathname, feed->child_argv);

                _exit(1);
            }
        }
    }
}

/* open a listening socket */
static int socket_open_listen(struct sockaddr_in *my_addr)
{
    int server_fd, tmp;

    server_fd = socket(AF_INET,SOCK_STREAM,0);
    if (server_fd < 0) {
        perror ("socket");
        return -1;
    }
        
    tmp = 1;
    setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &tmp, sizeof(tmp));

    if (bind (server_fd, (struct sockaddr *) my_addr, sizeof (*my_addr)) < 0) {
        char bindmsg[32];
        snprintf(bindmsg, sizeof(bindmsg), "bind(port %d)", ntohs(my_addr->sin_port));
        perror (bindmsg);
        close(server_fd);
        return -1;
    }
  
    if (listen (server_fd, 5) < 0) {
        perror ("listen");
        close(server_fd);
        return -1;
    }
    fcntl(server_fd, F_SETFL, O_NONBLOCK);

    return server_fd;
}

/* start all multicast streams */
static void start_multicast(void)
{
    FFStream *stream;
    char session_id[32];
    HTTPContext *rtp_c;
    struct sockaddr_in dest_addr;
    int default_port, stream_index;

    default_port = 6000;
    for(stream = first_stream; stream != NULL; stream = stream->next) {
        if (stream->is_multicast) {
            /* open the RTP connection */
            snprintf(session_id, sizeof(session_id), 
                     "%08x%08x", (int)random(), (int)random());

            /* choose a port if none given */
            if (stream->multicast_port == 0) {
                stream->multicast_port = default_port;
                default_port += 100;
            }

            dest_addr.sin_family = AF_INET;
            dest_addr.sin_addr = stream->multicast_ip;
            dest_addr.sin_port = htons(stream->multicast_port);

            rtp_c = rtp_new_connection(&dest_addr, stream, session_id);
            if (!rtp_c) {
                continue;
            }
            if (open_input_stream(rtp_c, "") < 0) {
                fprintf(stderr, "Could not open input stream for stream '%s'\n", 
                        stream->filename);
                continue;
            }

            rtp_c->rtp_protocol = RTSP_PROTOCOL_RTP_UDP_MULTICAST;

            /* open each RTP stream */
            for(stream_index = 0; stream_index < stream->nb_streams; 
                stream_index++) {
                dest_addr.sin_port = htons(stream->multicast_port + 
                                           2 * stream_index);
                if (rtp_new_av_stream(rtp_c, stream_index, &dest_addr) < 0) {
                    fprintf(stderr, "Could not open output stream '%s/streamid=%d'\n", 
                            stream->filename, stream_index);
                    exit(1);
                }
            }

            /* change state to send data */
            rtp_c->state = HTTPSTATE_SEND_DATA;
        }
    }
}

/* main loop of the http server */
static int http_server(void)
{
    int server_fd, ret, rtsp_server_fd, delay, delay1;
    struct pollfd poll_table[HTTP_MAX_CONNECTIONS + 2], *poll_entry;
    HTTPContext *c, *c_next;

    server_fd = socket_open_listen(&my_http_addr);
    if (server_fd < 0)
        return -1;

    rtsp_server_fd = socket_open_listen(&my_rtsp_addr);
    if (rtsp_server_fd < 0)
        return -1;
    
    http_log("ffserver started.\n");

    start_children(first_feed);

    first_http_ctx = NULL;
    nb_connections = 0;
    first_http_ctx = NULL;

    start_multicast();

    for(;;) {
        poll_entry = poll_table;
        poll_entry->fd = server_fd;
        poll_entry->events = POLLIN;
        poll_entry++;

        poll_entry->fd = rtsp_server_fd;
        poll_entry->events = POLLIN;
        poll_entry++;

        /* wait for events on each HTTP handle */
        c = first_http_ctx;
        delay = 1000;
        while (c != NULL) {
            int fd;
            fd = c->fd;
            switch(c->state) {
            case HTTPSTATE_SEND_HEADER:
            case RTSPSTATE_SEND_REPLY:
                c->poll_entry = poll_entry;
                poll_entry->fd = fd;
                poll_entry->events = POLLOUT;
                poll_entry++;
                break;
            case HTTPSTATE_SEND_DATA_HEADER:
            case HTTPSTATE_SEND_DATA:
            case HTTPSTATE_SEND_DATA_TRAILER:
                if (!c->is_packetized) {
                    /* for TCP, we output as much as we can (may need to put a limit) */
                    c->poll_entry = poll_entry;
                    poll_entry->fd = fd;
                    poll_entry->events = POLLOUT;
                    poll_entry++;
                } else {
                    /* not strictly correct, but currently cannot add
                       more than one fd in poll entry */
                    delay = 0;
                }
                break;
            case HTTPSTATE_WAIT_REQUEST:
            case HTTPSTATE_RECEIVE_DATA:
            case HTTPSTATE_WAIT_FEED:
            case RTSPSTATE_WAIT_REQUEST:
                /* need to catch errors */
                c->poll_entry = poll_entry;
                poll_entry->fd = fd;
                poll_entry->events = POLLIN;/* Maybe this will work */
                poll_entry++;
                break;
            case HTTPSTATE_WAIT:
                c->poll_entry = NULL;
                delay1 = compute_send_delay(c);
                if (delay1 < delay)
                    delay = delay1;
                break;
            case HTTPSTATE_WAIT_SHORT:
                c->poll_entry = NULL;
                delay1 = 10; /* one tick wait XXX: 10 ms assumed */
                if (delay1 < delay)
                    delay = delay1;
                break;
            default:
                c->poll_entry = NULL;
                break;
            }
            c = c->next;
        }

        /* wait for an event on one connection. We poll at least every
           second to handle timeouts */
        do {
            ret = poll(poll_table, poll_entry - poll_table, delay);
        } while (ret == -1);
        
        cur_time = gettime_ms();

        if (need_to_start_children) {
            need_to_start_children = 0;
            start_children(first_feed);
        }

        /* now handle the events */
        for(c = first_http_ctx; c != NULL; c = c_next) {
            c_next = c->next;
            if (handle_connection(c) < 0) {
                /* close and free the connection */
                log_connection(c);
                close_connection(c);
            }
        }

        poll_entry = poll_table;
        /* new HTTP connection request ? */
        if (poll_entry->revents & POLLIN) {
            new_connection(server_fd, 0);
        }
        poll_entry++;
        /* new RTSP connection request ? */
        if (poll_entry->revents & POLLIN) {
            new_connection(rtsp_server_fd, 1);
        }
    }
}

/* start waiting for a new HTTP/RTSP request */
static void start_wait_request(HTTPContext *c, int is_rtsp)
{
    c->buffer_ptr = c->buffer;
    c->buffer_end = c->buffer + c->buffer_size - 1; /* leave room for '\0' */

    if (is_rtsp) {
        c->timeout = cur_time + RTSP_REQUEST_TIMEOUT;
        c->state = RTSPSTATE_WAIT_REQUEST;
    } else {
        c->timeout = cur_time + HTTP_REQUEST_TIMEOUT;
        c->state = HTTPSTATE_WAIT_REQUEST;
    }
}

static void new_connection(int server_fd, int is_rtsp)
{
    struct sockaddr_in from_addr;
    int fd, len;
    HTTPContext *c = NULL;

    len = sizeof(from_addr);
    fd = accept(server_fd, (struct sockaddr *)&from_addr, 
                &len);
    if (fd < 0)
        return;
    fcntl(fd, F_SETFL, O_NONBLOCK);

    /* XXX: should output a warning page when coming
       close to the connection limit */
    if (nb_connections >= nb_max_connections)
        goto fail;
    
    /* add a new connection */
    c = av_mallocz(sizeof(HTTPContext));
    if (!c)
        goto fail;
    
    c->next = first_http_ctx;
    first_http_ctx = c;
    c->fd = fd;
    c->poll_entry = NULL;
    c->from_addr = from_addr;
    c->buffer_size = IOBUFFER_INIT_SIZE;
    c->buffer = av_malloc(c->buffer_size);
    if (!c->buffer)
        goto fail;
    nb_connections++;
    
    start_wait_request(c, is_rtsp);

    return;

 fail:
    if (c) {
        av_free(c->buffer);
        av_free(c);
    }
    close(fd);
}

static void close_connection(HTTPContext *c)
{
    HTTPContext **cp, *c1;
    int i, nb_streams;
    AVFormatContext *ctx;
    URLContext *h;
    AVStream *st;

    /* remove connection from list */
    cp = &first_http_ctx;
    while ((*cp) != NULL) {
        c1 = *cp;
        if (c1 == c) {
            *cp = c->next;
        } else {
            cp = &c1->next;
        }
    }

    /* remove connection associated resources */
    if (c->fd >= 0)
        close(c->fd);
    if (c->fmt_in) {
        /* close each frame parser */
        for(i=0;i<c->fmt_in->nb_streams;i++) {
            st = c->fmt_in->streams[i];
            if (st->codec.codec) {
                avcodec_close(&st->codec);
            }
        }
        av_close_input_file(c->fmt_in);
    }

    /* free RTP output streams if any */
    nb_streams = 0;
    if (c->stream) 
        nb_streams = c->stream->nb_streams;
    
    for(i=0;i<nb_streams;i++) {
        ctx = c->rtp_ctx[i];
        if (ctx) {
            av_write_trailer(ctx);
            av_free(ctx);
        }
        h = c->rtp_handles[i];
        if (h) {
            url_close(h);
        }
    }

    if (c->stream)
        current_bandwidth -= c->stream->bandwidth;
    av_freep(&c->pb_buffer);
    av_free(c->buffer);
    av_free(c);
    nb_connections--;
}

static int handle_connection(HTTPContext *c)
{
    int len, ret;
    
    switch(c->state) {
    case HTTPSTATE_WAIT_REQUEST:
    case RTSPSTATE_WAIT_REQUEST:
        /* timeout ? */
        if ((c->timeout - cur_time) < 0)
            return -1;
        if (c->poll_entry->revents & (POLLERR | POLLHUP))
            return -1;

        /* no need to read if no events */
        if (!(c->poll_entry->revents & POLLIN))
            return 0;
        /* read the data */
        len = read(c->fd, c->buffer_ptr, c->buffer_end - c->buffer_ptr);
        if (len < 0) {
            if (errno != EAGAIN && errno != EINTR)
                return -1;
        } else if (len == 0) {
            return -1;
        } else {
            /* search for end of request. XXX: not fully correct since garbage could come after the end */
            UINT8 *ptr;
            c->buffer_ptr += len;
            ptr = c->buffer_ptr;
            if ((ptr >= c->buffer + 2 && !memcmp(ptr-2, "\n\n", 2)) ||
                (ptr >= c->buffer + 4 && !memcmp(ptr-4, "\r\n\r\n", 4))) {
                /* request found : parse it and reply */
                if (c->state == HTTPSTATE_WAIT_REQUEST) {
                    ret = http_parse_request(c);
                } else {
                    ret = rtsp_parse_request(c);
                }
                if (ret < 0)
                    return -1;
            } else if (ptr >= c->buffer_end) {
                /* request too long: cannot do anything */
                return -1;
            }
        }
        break;

    case HTTPSTATE_SEND_HEADER:
        if (c->poll_entry->revents & (POLLERR | POLLHUP))
            return -1;

        /* no need to write if no events */
        if (!(c->poll_entry->revents & POLLOUT))
            return 0;
        len = write(c->fd, c->buffer_ptr, c->buffer_end - c->buffer_ptr);
        if (len < 0) {
            if (errno != EAGAIN && errno != EINTR) {
                /* error : close connection */
                av_freep(&c->pb_buffer);
                return -1;
            }
        } else {
            c->buffer_ptr += len;
            if (c->stream)
                c->stream->bytes_served += len;
            c->data_count += len;
            if (c->buffer_ptr >= c->buffer_end) {
                av_freep(&c->pb_buffer);
                /* if error, exit */
                if (c->http_error) {
                    return -1;
                }
                /* all the buffer was sent : synchronize to the incoming stream */
                c->state = HTTPSTATE_SEND_DATA_HEADER;
                c->buffer_ptr = c->buffer_end = c->buffer;
            }
        }
        break;

    case HTTPSTATE_SEND_DATA:
    case HTTPSTATE_SEND_DATA_HEADER:
    case HTTPSTATE_SEND_DATA_TRAILER:
        /* for packetized output, we consider we can always write (the
           input streams sets the speed). It may be better to verify
           that we do not rely too much on the kernel queues */
        if (!c->is_packetized) {
            if (c->poll_entry->revents & (POLLERR | POLLHUP))
                return -1;
            
            /* no need to read if no events */
            if (!(c->poll_entry->revents & POLLOUT))
                return 0;
        }
        if (http_send_data(c) < 0)
            return -1;
        break;
    case HTTPSTATE_RECEIVE_DATA:
        /* no need to read if no events */
        if (c->poll_entry->revents & (POLLERR | POLLHUP))
            return -1;
        if (!(c->poll_entry->revents & POLLIN))
            return 0;
        if (http_receive_data(c) < 0)
            return -1;
        break;
    case HTTPSTATE_WAIT_FEED:
        /* no need to read if no events */
        if (c->poll_entry->revents & (POLLIN | POLLERR | POLLHUP))
            return -1;

        /* nothing to do, we'll be waken up by incoming feed packets */
        break;

    case HTTPSTATE_WAIT:
        /* if the delay expired, we can send new packets */
        if (compute_send_delay(c) <= 0)
            c->state = HTTPSTATE_SEND_DATA;
        break;
    case HTTPSTATE_WAIT_SHORT:
        /* just return back to send data */
        c->state = HTTPSTATE_SEND_DATA;
        break;

    case RTSPSTATE_SEND_REPLY:
        if (c->poll_entry->revents & (POLLERR | POLLHUP)) {
            av_freep(&c->pb_buffer);
            return -1;
        }
        /* no need to write if no events */
        if (!(c->poll_entry->revents & POLLOUT))
            return 0;
        len = write(c->fd, c->buffer_ptr, c->buffer_end - c->buffer_ptr);
        if (len < 0) {
            if (errno != EAGAIN && errno != EINTR) {
                /* error : close connection */
                av_freep(&c->pb_buffer);
                return -1;
            }
        } else {
            c->buffer_ptr += len;
            c->data_count += len;
            if (c->buffer_ptr >= c->buffer_end) {
                /* all the buffer was sent : wait for a new request */
                av_freep(&c->pb_buffer);
                start_wait_request(c, 1);
            }
        }
        break;
    case HTTPSTATE_READY:
        /* nothing to do */
        break;
    default:
        return -1;
    }
    return 0;
}

static int extract_rates(char *rates, int ratelen, const char *request)
{
    const char *p;

    for (p = request; *p && *p != '\r' && *p != '\n'; ) {
        if (strncasecmp(p, "Pragma:", 7) == 0) {
            const char *q = p + 7;

            while (*q && *q != '\n' && isspace(*q))
                q++;

            if (strncasecmp(q, "stream-switch-entry=", 20) == 0) {
                int stream_no;
                int rate_no;

                q += 20;

                memset(rates, 0xff, ratelen);

                while (1) {
                    while (*q && *q != '\n' && *q != ':')
                        q++;

                    if (sscanf(q, ":%d:%d", &stream_no, &rate_no) != 2) {
                        break;
                    }
                    stream_no--;
                    if (stream_no < ratelen && stream_no >= 0) {
                        rates[stream_no] = rate_no;
                    }

                    while (*q && *q != '\n' && !isspace(*q))
                        q++;
                }

                return 1;
            }
        }
        p = strchr(p, '\n');
        if (!p)
            break;

        p++;
    }

    return 0;
}

static int find_stream_in_feed(FFStream *feed, AVCodecContext *codec, int bit_rate)
{
    int i;
    int best_bitrate = 100000000;
    int best = -1;

    for (i = 0; i < feed->nb_streams; i++) {
        AVCodecContext *feed_codec = &feed->streams[i]->codec;

        if (feed_codec->codec_id != codec->codec_id ||
            feed_codec->sample_rate != codec->sample_rate ||
            feed_codec->width != codec->width ||
            feed_codec->height != codec->height) {
            continue;
        }

        /* Potential stream */

        /* We want the fastest stream less than bit_rate, or the slowest 
         * faster than bit_rate
         */

        if (feed_codec->bit_rate <= bit_rate) {
            if (best_bitrate > bit_rate || feed_codec->bit_rate > best_bitrate) {
                best_bitrate = feed_codec->bit_rate;
                best = i;
            }
        } else {
            if (feed_codec->bit_rate < best_bitrate) {
                best_bitrate = feed_codec->bit_rate;
                best = i;
            }
        }
    }

    return best;
}

static int modify_current_stream(HTTPContext *c, char *rates)
{
    int i;
    FFStream *req = c->stream;
    int action_required = 0;

    /* Not much we can do for a feed */