summaryrefslogtreecommitdiff
path: root/libavformat/mmst.c
blob: 0a728eb35f9e86a491c19b7d9a3f9d4a8912955b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
/*
 * MMS protocol over TCP
 * Copyright (c) 2006,2007 Ryan Martell
 * Copyright (c) 2007 Björn Axelsson
 * Copyright (c) 2010 Zhentan Feng <spyfeng at gmail dot com>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg 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.
 *
 * FFmpeg 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 FFmpeg; 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, const 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_FLAG_READ_WRITE,
                     &h->interrupt_callback, NULL);
    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 = {
    .name      = "mmst",
    .url_open  = mms_open,
    .url_read  = mms_read,
    .url_close = mms_close,
};