PeerStreamer

/*

 * MMS protocol over TCP

 * Copyright (c) 2006,2007 Ryan Martell

 * Copyright (c) 2007 Bj?rn Axelsson

 * Copyright (c) 2010 Zhentan Feng <spyfeng at gmail dot com>

 *

 * 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

 */

/* References

 * MMS protocol specification:

 *  [1]http://msdn.microsoft.com/en-us/library/cc234711(PROT.10).aspx

 * ASF specification. Revision 01.20.03.

 *  [2]http://msdn.microsoft.com/en-us/library/bb643323.aspx

 */

#include "avformat.h"

#include "mms.h"

#include "internal.h"

#include "avio_internal.h"

#include "libavutil/intreadwrite.h"

#include "libavcodec/bytestream.h"

#include "network.h"

#include "url.h"

#define LOCAL_ADDRESS 0xc0a80081    // FIXME get and use correct local ip address.

#define LOCAL_PORT    1037          // as above.

/** Client to server packet types. */

typedef enum {

    CS_PKT_INITIAL                  = 0x01,

    CS_PKT_PROTOCOL_SELECT          = 0x02,

    CS_PKT_MEDIA_FILE_REQUEST       = 0x05,

    CS_PKT_START_FROM_PKT_ID        = 0x07,

    CS_PKT_STREAM_PAUSE             = 0x09,

    CS_PKT_STREAM_CLOSE             = 0x0d,

    CS_PKT_MEDIA_HEADER_REQUEST     = 0x15,

    CS_PKT_TIMING_DATA_REQUEST      = 0x18,

    CS_PKT_USER_PASSWORD            = 0x1a,

    CS_PKT_KEEPALIVE                = 0x1b,

    CS_PKT_STREAM_ID_REQUEST        = 0x33,

} MMSCSPacketType;

/** Server to client packet types. */

typedef enum {

    /** Control packets. */

    /*@{*/

    SC_PKT_CLIENT_ACCEPTED          = 0x01,

    SC_PKT_PROTOCOL_ACCEPTED        = 0x02,

    SC_PKT_PROTOCOL_FAILED          = 0x03,

    SC_PKT_MEDIA_PKT_FOLLOWS        = 0x05,

    SC_PKT_MEDIA_FILE_DETAILS       = 0x06,

    SC_PKT_HEADER_REQUEST_ACCEPTED  = 0x11,

    SC_PKT_TIMING_TEST_REPLY        = 0x15,

    SC_PKT_PASSWORD_REQUIRED        = 0x1a,

    SC_PKT_KEEPALIVE                = 0x1b,

    SC_PKT_STREAM_STOPPED           = 0x1e,

    SC_PKT_STREAM_CHANGING          = 0x20,

    SC_PKT_STREAM_ID_ACCEPTED       = 0x21,

    /*@}*/

    /** Pseudo packets. */

    /*@{*/

    SC_PKT_CANCEL                   = -1,

    SC_PKT_NO_DATA                  = -2,

    /*@}*/

    /** Data packets. */

    /*@{*/

    SC_PKT_ASF_HEADER               = 0x010000,// make it bigger than 0xFF in case of

    SC_PKT_ASF_MEDIA                = 0x010001,// receiving false data packets.

    /*@}*/

} MMSSCPacketType;

typedef struct {

    MMSContext  mms;

    int outgoing_packet_seq;             ///< Outgoing packet sequence number.

    char path[256];                      ///< Path of the resource being asked for.

    char host[128];                      ///< Host of the resources.

    int incoming_packet_seq;             ///< Incoming packet sequence number.

    int incoming_flags;                  ///< Incoming packet flags.

    int packet_id;                       ///< Identifier for packets in the current stream.

    unsigned int header_packet_id;       ///< default is 2.

} MMSTContext;

/** Create MMST command packet header */

static void start_command_packet(MMSTContext *mmst, MMSCSPacketType packet_type)

{

    MMSContext *mms    = &mmst->mms;

    mms->write_out_ptr = mms->out_buffer;

    bytestream_put_le32(&mms->write_out_ptr, 1); // start sequence

    bytestream_put_le32(&mms->write_out_ptr, 0xb00bface);

    bytestream_put_le32(&mms->write_out_ptr, 0); // Length starts from after the protocol type bytes

    bytestream_put_le32(&mms->write_out_ptr, MKTAG('M','M','S',' '));

    bytestream_put_le32(&mms->write_out_ptr, 0);

    bytestream_put_le32(&mms->write_out_ptr, mmst->outgoing_packet_seq++);

    bytestream_put_le64(&mms->write_out_ptr, 0); // timestamp

    bytestream_put_le32(&mms->write_out_ptr, 0);

    bytestream_put_le16(&mms->write_out_ptr, packet_type);

    bytestream_put_le16(&mms->write_out_ptr, 3); // direction to server

}

/** Add prefixes to MMST command packet. */

static void insert_command_prefixes(MMSContext *mms,

        uint32_t prefix1, uint32_t prefix2)

{

    bytestream_put_le32(&mms->write_out_ptr, prefix1); // first prefix

    bytestream_put_le32(&mms->write_out_ptr, prefix2); // second prefix

}

/** Send a prepared MMST command packet. */

static int send_command_packet(MMSTContext *mmst)

{

    MMSContext *mms  = &mmst->mms;

    int len= mms->write_out_ptr - mms->out_buffer;

    int exact_length = FFALIGN(len, 8);

    int first_length= exact_length - 16;

    int len8= first_length/8;

    int write_result;

    // update packet length fields.

    AV_WL32(mms->out_buffer + 8, first_length);

    AV_WL32(mms->out_buffer + 16, len8);

    AV_WL32(mms->out_buffer + 32, len8-2);

    memset(mms->write_out_ptr, 0, exact_length - len);

    // write it out.

    write_result= ffurl_write(mms->mms_hd, mms->out_buffer, exact_length);

    if(write_result != exact_length) {

        av_log(NULL, AV_LOG_ERROR,

               "Failed to write data of length %d: %d (%s)\n",

               exact_length, write_result,

               write_result < 0 ? strerror(write_result) :

                   "The server closed the connection");

        return AVERROR(EIO);

    }

    return 0;

}

static void mms_put_utf16(MMSContext *mms, uint8_t *src)

{

    AVIOContext bic;

    int size = mms->write_out_ptr - mms->out_buffer;

    int len;

    ffio_init_context(&bic, mms->write_out_ptr,

            sizeof(mms->out_buffer) - size, 1, NULL, NULL, NULL, NULL);

    len = avio_put_str16le(&bic, src);

    mms->write_out_ptr += len;

}

static int send_time_test_data(MMSTContext *mmst)

{

    start_command_packet(mmst, CS_PKT_TIMING_DATA_REQUEST);

    insert_command_prefixes(&mmst->mms, 0x00f0f0f0, 0x0004000b);

    return send_command_packet(mmst);

}

static int send_protocol_select(MMSTContext *mmst)

{

    char data_string[256];

    MMSContext *mms = &mmst->mms;

    start_command_packet(mmst, CS_PKT_PROTOCOL_SELECT);

    insert_command_prefixes(mms, 0, 0xffffffff);

    bytestream_put_le32(&mms->write_out_ptr, 0);          // maxFunnelBytes

    bytestream_put_le32(&mms->write_out_ptr, 0x00989680); // maxbitRate

    bytestream_put_le32(&mms->write_out_ptr, 2);          // funnelMode

    snprintf(data_string, sizeof(data_string), "\\\\%d.%d.%d.%d\\%s\\%d",

            (LOCAL_ADDRESS>>24)&0xff,

            (LOCAL_ADDRESS>>16)&0xff,

            (LOCAL_ADDRESS>>8)&0xff,

            LOCAL_ADDRESS&0xff,

            "TCP",                                        // or UDP

            LOCAL_PORT);

    mms_put_utf16(mms, data_string);

    return send_command_packet(mmst);

}

static int send_media_file_request(MMSTContext *mmst)

{

    MMSContext *mms = &mmst->mms;

    start_command_packet(mmst, CS_PKT_MEDIA_FILE_REQUEST);

    insert_command_prefixes(mms, 1, 0xffffffff);

    bytestream_put_le32(&mms->write_out_ptr, 0);

    bytestream_put_le32(&mms->write_out_ptr, 0);

    mms_put_utf16(mms, mmst->path + 1); // +1 for skip "/"

    return send_command_packet(mmst);

}

static void handle_packet_stream_changing_type(MMSTContext *mmst)

{

    MMSContext *mms = &mmst->mms;

    av_dlog(NULL, "Stream changing!\n");

    // 40 is the packet header size, 7 is the prefix size.

    mmst->header_packet_id= AV_RL32(mms->in_buffer + 40 + 7);

    av_dlog(NULL, "Changed header prefix to 0x%x", mmst->header_packet_id);

}

static int send_keepalive_packet(MMSTContext *mmst)

{

    // respond to a keepalive with a keepalive...

    start_command_packet(mmst, CS_PKT_KEEPALIVE);

    insert_command_prefixes(&mmst->mms, 1, 0x100FFFF);

    return send_command_packet(mmst);

}

/** Pad media packets smaller than max_packet_size and/or adjust read position

  * after a seek. */

static void pad_media_packet(MMSContext *mms)

{

    if(mms->remaining_in_len<mms->asf_packet_len) {

        int padding_size = mms->asf_packet_len - mms->remaining_in_len;

        memset(mms->in_buffer + mms->remaining_in_len, 0, padding_size);

        mms->remaining_in_len += padding_size;

    }

}

/** Read incoming MMST media, header or command packet. */

static MMSSCPacketType get_tcp_server_response(MMSTContext *mmst)

{

    int read_result;

    MMSSCPacketType packet_type= -1;

    MMSContext *mms = &mmst->mms;

    for(;;) {

        read_result = ffurl_read_complete(mms->mms_hd, mms->in_buffer, 8);

        if (read_result != 8) {

            if(read_result < 0) {

                av_log(NULL, AV_LOG_ERROR,

                       "Error reading packet header: %d (%s)\n",

                       read_result, strerror(read_result));

                packet_type = SC_PKT_CANCEL;

            } else {

                av_log(NULL, AV_LOG_ERROR,

                       "The server closed the connection\n");

                packet_type = SC_PKT_NO_DATA;

            }

            return packet_type;

        }

        // handle command packet.

        if(AV_RL32(mms->in_buffer + 4)==0xb00bface) {

            int length_remaining, hr;

            mmst->incoming_flags= mms->in_buffer[3];

            read_result= ffurl_read_complete(mms->mms_hd, mms->in_buffer+8, 4);

            if(read_result != 4) {

                av_log(NULL, AV_LOG_ERROR,

                       "Reading command packet length failed: %d (%s)\n",

                       read_result,

                       read_result < 0 ? strerror(read_result) :

                           "The server closed the connection");

                return read_result < 0 ? read_result : AVERROR(EIO);

            }

            length_remaining= AV_RL32(mms->in_buffer+8) + 4;

            av_dlog(NULL, "Length remaining is %d\n", length_remaining);

            // read the rest of the packet.

            if (length_remaining < 0

                || length_remaining > sizeof(mms->in_buffer) - 12) {

                av_log(NULL, AV_LOG_ERROR,

                       "Incoming packet length %d exceeds bufsize %zu\n",

                       length_remaining, sizeof(mms->in_buffer) - 12);

                return AVERROR_INVALIDDATA;

            }

            read_result = ffurl_read_complete(mms->mms_hd, mms->in_buffer + 12,

                                            length_remaining) ;

            if (read_result != length_remaining) {

                av_log(NULL, AV_LOG_ERROR,

                       "Reading pkt data (length=%d) failed: %d (%s)\n",

                       length_remaining, read_result,

                       read_result < 0 ? strerror(read_result) :

                           "The server closed the connection");

                return read_result < 0 ? read_result : AVERROR(EIO);

            }

            packet_type= AV_RL16(mms->in_buffer+36);

            if (read_result >= 44 && (hr = AV_RL32(mms->in_buffer + 40))) {

                av_log(NULL, AV_LOG_ERROR,

                       "Server sent a message with packet type 0x%x and error status code 0x%08x\n", packet_type, hr);

                return AVERROR(EINVAL);

            }

        } else {

            int length_remaining;

            int packet_id_type;

            int tmp;

            // note we cache the first 8 bytes,

            // then fill up the buffer with the others

            tmp                       = AV_RL16(mms->in_buffer + 6);

            length_remaining          = (tmp - 8) & 0xffff;

            mmst->incoming_packet_seq = AV_RL32(mms->in_buffer);

            packet_id_type            = mms->in_buffer[4];

            mmst->incoming_flags      = mms->in_buffer[5];

            if (length_remaining < 0

                || length_remaining > sizeof(mms->in_buffer) - 8) {

                av_log(NULL, AV_LOG_ERROR,

                       "Data length %d is invalid or too large (max=%zu)\n",

                       length_remaining, sizeof(mms->in_buffer));

                return AVERROR_INVALIDDATA;

            }

            mms->remaining_in_len    = length_remaining;

            mms->read_in_ptr         = mms->in_buffer;

            read_result= ffurl_read_complete(mms->mms_hd, mms->in_buffer, length_remaining);

            if(read_result != length_remaining) {

                av_log(NULL, AV_LOG_ERROR,

                       "Failed to read packet data of size %d: %d (%s)\n",

                       length_remaining, read_result,

                       read_result < 0 ? strerror(read_result) :

                           "The server closed the connection");

                return read_result < 0 ? read_result : AVERROR(EIO);

            }

            // if we successfully read everything.

            if(packet_id_type == mmst->header_packet_id) {

                packet_type = SC_PKT_ASF_HEADER;

                // Store the asf header

                if(!mms->header_parsed) {

                    void *p = av_realloc(mms->asf_header,

                                  mms->asf_header_size + mms->remaining_in_len);

                    if (!p) {

                        av_freep(&mms->asf_header);

                        return AVERROR(ENOMEM);

                    }

                    mms->asf_header = p;

                    memcpy(mms->asf_header + mms->asf_header_size,

                           mms->read_in_ptr, mms->remaining_in_len);

                    mms->asf_header_size += mms->remaining_in_len;

                }

                // 0x04 means asf header is sent in multiple packets.

                if (mmst->incoming_flags == 0x04)

                    continue;

            } else if(packet_id_type == mmst->packet_id) {

                packet_type = SC_PKT_ASF_MEDIA;

            } else {

                av_dlog(NULL, "packet id type %d is old.", packet_id_type);

                continue;

            }

        }

        // preprocess some packet type

        if(packet_type == SC_PKT_KEEPALIVE) {

            send_keepalive_packet(mmst);

            continue;

        } else if(packet_type == SC_PKT_STREAM_CHANGING) {

            handle_packet_stream_changing_type(mmst);

        } else if(packet_type == SC_PKT_ASF_MEDIA) {

            pad_media_packet(mms);

        }

        return packet_type;

    }

}

static int mms_safe_send_recv(MMSTContext *mmst,

                              int (*send_fun)(MMSTContext *mmst),

                              const MMSSCPacketType expect_type)

{

    MMSSCPacketType type;

    if(send_fun) {

        int ret = send_fun(mmst);

        if (ret < 0) {

            av_dlog(NULL, "Send Packet error before expecting recv packet %d\n", expect_type);

            return ret;

        }

    }

    if ((type = get_tcp_server_response(mmst)) != expect_type) {

        av_log(NULL, AV_LOG_ERROR,

               "Corrupt stream (unexpected packet type 0x%x, expected 0x%x)\n",

               type, expect_type);

        return AVERROR_INVALIDDATA;

    } else {

        return 0;

    }

}

static int send_media_header_request(MMSTContext *mmst)

{

    MMSContext *mms = &mmst->mms;

    start_command_packet(mmst, CS_PKT_MEDIA_HEADER_REQUEST);

    insert_command_prefixes(mms, 1, 0);

    bytestream_put_le32(&mms->write_out_ptr, 0);

    bytestream_put_le32(&mms->write_out_ptr, 0x00800000);

    bytestream_put_le32(&mms->write_out_ptr, 0xffffffff);

    bytestream_put_le32(&mms->write_out_ptr, 0);

    bytestream_put_le32(&mms->write_out_ptr, 0);

    bytestream_put_le32(&mms->write_out_ptr, 0);

    // the media preroll value in milliseconds?

    bytestream_put_le32(&mms->write_out_ptr, 0);

    bytestream_put_le32(&mms->write_out_ptr, 0x40AC2000);

    bytestream_put_le32(&mms->write_out_ptr, 2);

    bytestream_put_le32(&mms->write_out_ptr, 0);

    return send_command_packet(mmst);

}

/** Send the initial handshake. */

static int send_startup_packet(MMSTContext *mmst)

{

    char data_string[256];

    MMSContext *mms = &mmst->mms;

    // SubscriberName is defined in MS specification linked below.

    // The guid value can be any valid value.

    // http://download.microsoft.com/

    // download/9/5/E/95EF66AF-9026-4BB0-A41D-A4F81802D92C/%5BMS-WMSP%5D.pdf

    snprintf(data_string, sizeof(data_string),

            "NSPlayer/7.0.0.1956; {%s}; Host: %s",

            "7E667F5D-A661-495E-A512-F55686DDA178", mmst->host);

    start_command_packet(mmst, CS_PKT_INITIAL);

    insert_command_prefixes(mms, 0, 0x0004000b);

    bytestream_put_le32(&mms->write_out_ptr, 0x0003001c);

    mms_put_utf16(mms, data_string);

    return send_command_packet(mmst);

}

/** Send MMST stream selection command based on the AVStream->discard values. */

static int send_stream_selection_request(MMSTContext *mmst)

{

    int i;

    MMSContext *mms = &mmst->mms;

    //  send the streams we want back...

    start_command_packet(mmst, CS_PKT_STREAM_ID_REQUEST);

    bytestream_put_le32(&mms->write_out_ptr, mms->stream_num);         // stream nums

    for(i= 0; i<mms->stream_num; i++) {

        bytestream_put_le16(&mms->write_out_ptr, 0xffff);              // flags

        bytestream_put_le16(&mms->write_out_ptr, mms->streams[i].id);  // stream id

        bytestream_put_le16(&mms->write_out_ptr, 0);                   // selection

    }

    return send_command_packet(mmst);

}

static int send_close_packet(MMSTContext *mmst)

{

    start_command_packet(mmst, CS_PKT_STREAM_CLOSE);

    insert_command_prefixes(&mmst->mms, 1, 1);

    return send_command_packet(mmst);

}

/** Close the MMSH/MMST connection */

static int mms_close(URLContext *h)

{

    MMSTContext *mmst = (MMSTContext *)h->priv_data;

    MMSContext *mms   = &mmst->mms;

    if(mms->mms_hd) {

        send_close_packet(mmst);

        ffurl_close(mms->mms_hd);

    }

    /* free all separately allocated pointers in mms */

    av_free(mms->streams);

    av_free(mms->asf_header);

    av_freep(&h->priv_data);

    return 0;

}

static int send_media_packet_request(MMSTContext *mmst)

{

    MMSContext *mms = &mmst->mms;

    start_command_packet(mmst, CS_PKT_START_FROM_PKT_ID);

    insert_command_prefixes(mms, 1, 0x0001FFFF);

    bytestream_put_le64(&mms->write_out_ptr, 0);          // seek timestamp

    bytestream_put_le32(&mms->write_out_ptr, 0xffffffff); // unknown

    bytestream_put_le32(&mms->write_out_ptr, 0xffffffff); // packet offset

    bytestream_put_byte(&mms->write_out_ptr, 0xff);       // max stream time limit

    bytestream_put_byte(&mms->write_out_ptr, 0xff);       // max stream time limit

    bytestream_put_byte(&mms->write_out_ptr, 0xff);       // max stream time limit

    bytestream_put_byte(&mms->write_out_ptr, 0x00);       // stream time limit flag

    mmst->packet_id++;                                     // new packet_id

    bytestream_put_le32(&mms->write_out_ptr, mmst->packet_id);

    return send_command_packet(mmst);

}

static void clear_stream_buffers(MMSContext *mms)

{

    mms->remaining_in_len = 0;

    mms->read_in_ptr      = mms->in_buffer;

}

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

{

    MMSTContext *mmst;

    MMSContext *mms;

    int port, err;

    char tcpname[256];

    h->is_streamed = 1;

    mmst = h->priv_data = av_mallocz(sizeof(MMSTContext));

    if (!h->priv_data)

        return AVERROR(ENOMEM);

    mms = &mmst->mms;

    // only for MMS over TCP, so set proto = NULL

    av_url_split(NULL, 0, NULL, 0,

            mmst->host, sizeof(mmst->host), &port, mmst->path,

            sizeof(mmst->path), uri);

    if(port<0)

        port = 1755; // defaut mms protocol port

    // establish tcp connection.

    ff_url_join(tcpname, sizeof(tcpname), "tcp", NULL, mmst->host, port, NULL);

    err = ffurl_open(&mms->mms_hd, tcpname, AVIO_RDWR);

    if (err)

        goto fail;

    mmst->packet_id        = 3;          // default, initial value.

    mmst->header_packet_id = 2;          // default, initial value.

    err = mms_safe_send_recv(mmst, send_startup_packet, SC_PKT_CLIENT_ACCEPTED);

    if (err)

        goto fail;

    err = mms_safe_send_recv(mmst, send_time_test_data, SC_PKT_TIMING_TEST_REPLY);

    if (err)

        goto fail;

    err = mms_safe_send_recv(mmst, send_protocol_select, SC_PKT_PROTOCOL_ACCEPTED);

    if (err)

        goto fail;

    err = mms_safe_send_recv(mmst, send_media_file_request, SC_PKT_MEDIA_FILE_DETAILS);

    if (err)

        goto fail;

    err = mms_safe_send_recv(mmst, send_media_header_request, SC_PKT_HEADER_REQUEST_ACCEPTED);

    if (err)

        goto fail;

    err = mms_safe_send_recv(mmst, NULL, SC_PKT_ASF_HEADER);

    if (err)

        goto fail;

    if((mmst->incoming_flags != 0X08) && (mmst->incoming_flags != 0X0C)) {

        av_log(NULL, AV_LOG_ERROR,

               "The server does not support MMST (try MMSH or RTSP)\n");

        err = AVERROR(EINVAL);

        goto fail;

    }

    err = ff_mms_asf_header_parser(mms);

    if (err) {

        av_dlog(NULL, "asf header parsed failed!\n");

        goto fail;

    }

    mms->header_parsed = 1;

    if (!mms->asf_packet_len || !mms->stream_num)

        goto fail;

    clear_stream_buffers(mms);

    err = mms_safe_send_recv(mmst, send_stream_selection_request, SC_PKT_STREAM_ID_ACCEPTED);

    if (err)

        goto fail;

    // send media packet request

    err = mms_safe_send_recv(mmst, send_media_packet_request, SC_PKT_MEDIA_PKT_FOLLOWS);

    if (err) {

        goto fail;

    }

    av_dlog(NULL, "Leaving open (success)\n");

    return 0;

fail:

    mms_close(h);

    av_dlog(NULL, "Leaving open (failure: %d)\n", err);

    return err;

}

/** Read ASF data through the protocol. */

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

{

    /* TODO: see tcp.c:tcp_read() about a possible timeout scheme */

    MMSTContext *mmst = h->priv_data;

    MMSContext *mms   = &mmst->mms;

    int result = 0;

    do {

        if(mms->asf_header_read_size < mms->asf_header_size) {

            /* Read from ASF header buffer */

            result = ff_mms_read_header(mms, buf, size);

        } else if(mms->remaining_in_len) {

            /* Read remaining packet data to buffer.

             * the result can not be zero because remaining_in_len is positive.*/

            result = ff_mms_read_data(mms, buf, size);

        } else {

            /* Read from network */

            int err = mms_safe_send_recv(mmst, NULL, SC_PKT_ASF_MEDIA);

            if (err == 0) {

                if(mms->remaining_in_len>mms->asf_packet_len) {

                    av_log(NULL, AV_LOG_ERROR,

                           "Incoming pktlen %d is larger than ASF pktsize %d\n",

                           mms->remaining_in_len, mms->asf_packet_len);

                    result= AVERROR(EIO);

                } else {

                    // copy the data to the packet buffer.

                    result = ff_mms_read_data(mms, buf, size);

                    if (result == 0) {

                        av_dlog(NULL, "read asf media paket size is zero!\n");

                        break;

                    }

                }

            } else {

                av_dlog(NULL, "read packet error!\n");

                break;

            }

        }

    } while(!result); // only return one packet.

    return result;

}

URLProtocol ff_mmst_protocol = {

    "mmst",

    mms_open,

    mms_read,

    NULL, // write

    NULL, // seek

    mms_close,

};