3 * Copyright (c) 2009 Bartlomiej Wolowiec
4 * Copyright (c) 2010 Anssi Hannula
5 * Copyright (c) 2010 Carl Eugen Hoyos
7 * This file is part of FFmpeg.
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 * IEC-61937 encapsulation of various formats, used by S/PDIF
27 * @author Bartlomiej Wolowiec
28 * @author Anssi Hannula
29 * @author Carl Eugen Hoyos
33 * Terminology used in specification:
34 * data-burst - IEC61937 frame, contains header and encapsuled frame
35 * burst-preambule - IEC61937 frame header, contains 16-bits words named Pa, Pb, Pc and Pd
36 * burst-payload - encapsuled frame
37 * Pa, Pb - syncword - 0xF872, 0x4E1F
38 * Pc - burst-info, contains data-type (bits 0-6), error flag (bit 7), data-type-dependent info (bits 8-12)
39 * and bitstream number (bits 13-15)
40 * data-type - determines type of encapsuled frames
41 * Pd - length code (number of bits or bytes of encapsuled frame - according to data_type)
43 * IEC 61937 frames at normal usage start every specific count of bytes,
44 * dependent from data-type (spaces between packets are filled by zeros)
50 #include "avio_internal.h"
52 #include "libavcodec/ac3.h"
53 #include "libavcodec/dca.h"
54 #include "libavcodec/aacadtsdec.h"
55 #include "libavutil/opt.h"
57 typedef struct IEC61937Context
{
58 const AVClass
*av_class
;
59 enum IEC61937DataType data_type
;///< burst info - reference to type of payload of the data-burst
60 int length_code
; ///< length code in bits or bytes, depending on data type
61 int pkt_offset
; ///< data burst repetition period in bytes
62 uint8_t *buffer
; ///< allocated buffer, used for swap bytes
63 int buffer_size
; ///< size of allocated buffer
65 uint8_t *out_buf
; ///< pointer to the outgoing data before byte-swapping
66 int out_bytes
; ///< amount of outgoing bytes
68 int use_preamble
; ///< preamble enabled (disabled for exactly pre-padded DTS)
69 int extra_bswap
; ///< extra bswap for payload (for LE DTS => standard BE DTS)
71 uint8_t *hd_buf
; ///< allocated buffer to concatenate hd audio frames
72 int hd_buf_size
; ///< size of the hd audio buffer
73 int hd_buf_count
; ///< number of frames in the hd audio buffer
74 int hd_buf_filled
; ///< amount of bytes in the hd audio buffer
76 int dtshd_skip
; ///< counter used for skipping DTS-HD frames
81 #define SPDIF_FLAG_BIGENDIAN 0x01
84 /// function, which generates codec dependent header information.
85 /// Sets data_type and pkt_offset, and length_code, out_bytes, out_buf if necessary
86 int (*header_info
) (AVFormatContext
*s
, AVPacket
*pkt
);
89 static const AVOption options
[] = {
90 { "spdif_flags", "IEC 61937 encapsulation flags", offsetof(IEC61937Context
, spdif_flags
), AV_OPT_TYPE_FLAGS
, {.i64
= 0}, 0, INT_MAX
, AV_OPT_FLAG_ENCODING_PARAM
, "spdif_flags" },
91 { "be", "output in big-endian format (for use as s16be)", 0, AV_OPT_TYPE_CONST
, {.i64
= SPDIF_FLAG_BIGENDIAN
}, 0, INT_MAX
, AV_OPT_FLAG_ENCODING_PARAM
, "spdif_flags" },
92 { "dtshd_rate", "mux complete DTS frames in HD mode at the specified IEC958 rate (in Hz, default 0=disabled)", offsetof(IEC61937Context
, dtshd_rate
), AV_OPT_TYPE_INT
, {.i64
= 0}, 0, 768000, AV_OPT_FLAG_ENCODING_PARAM
},
93 { "dtshd_fallback_time", "min secs to strip HD for after an overflow (-1: till the end, default 60)", offsetof(IEC61937Context
, dtshd_fallback
), AV_OPT_TYPE_INT
, {.i64
= 60}, -1, INT_MAX
, AV_OPT_FLAG_ENCODING_PARAM
},
97 static const AVClass spdif_class
= {
98 .class_name
= "spdif",
99 .item_name
= av_default_item_name
,
101 .version
= LIBAVUTIL_VERSION_INT
,
104 static int spdif_header_ac3(AVFormatContext
*s
, AVPacket
*pkt
)
106 IEC61937Context
*ctx
= s
->priv_data
;
107 int bitstream_mode
= pkt
->data
[5] & 0x7;
109 ctx
->data_type
= IEC61937_AC3
| (bitstream_mode
<< 8);
110 ctx
->pkt_offset
= AC3_FRAME_SIZE
<< 2;
114 static int spdif_header_eac3(AVFormatContext
*s
, AVPacket
*pkt
)
116 IEC61937Context
*ctx
= s
->priv_data
;
117 static const uint8_t eac3_repeat
[4] = {6, 3, 2, 1};
120 if ((pkt
->data
[4] & 0xc0) != 0xc0) /* fscod */
121 repeat
= eac3_repeat
[(pkt
->data
[4] & 0x30) >> 4]; /* numblkscod */
123 ctx
->hd_buf
= av_fast_realloc(ctx
->hd_buf
, &ctx
->hd_buf_size
, ctx
->hd_buf_filled
+ pkt
->size
);
125 return AVERROR(ENOMEM
);
127 memcpy(&ctx
->hd_buf
[ctx
->hd_buf_filled
], pkt
->data
, pkt
->size
);
129 ctx
->hd_buf_filled
+= pkt
->size
;
130 if (++ctx
->hd_buf_count
< repeat
){
134 ctx
->data_type
= IEC61937_EAC3
;
135 ctx
->pkt_offset
= 24576;
136 ctx
->out_buf
= ctx
->hd_buf
;
137 ctx
->out_bytes
= ctx
->hd_buf_filled
;
138 ctx
->length_code
= ctx
->hd_buf_filled
;
140 ctx
->hd_buf_count
= 0;
141 ctx
->hd_buf_filled
= 0;
146 * DTS type IV (DTS-HD) can be transmitted with various frame repetition
147 * periods; longer repetition periods allow for longer packets and therefore
148 * higher bitrate. Longer repetition periods mean that the constant bitrate of
149 * the outputted IEC 61937 stream is higher.
150 * The repetition period is measured in IEC 60958 frames (4 bytes).
152 static int spdif_dts4_subtype(int period
)
155 case 512: return 0x0;
156 case 1024: return 0x1;
157 case 2048: return 0x2;
158 case 4096: return 0x3;
159 case 8192: return 0x4;
160 case 16384: return 0x5;
165 static int spdif_header_dts4(AVFormatContext
*s
, AVPacket
*pkt
, int core_size
,
166 int sample_rate
, int blocks
)
168 IEC61937Context
*ctx
= s
->priv_data
;
169 static const char dtshd_start_code
[10] = { 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfe, 0xfe };
170 int pkt_size
= pkt
->size
;
175 av_log(s
, AV_LOG_ERROR
, "HD mode not supported for this format\n");
176 return AVERROR(EINVAL
);
180 av_log(s
, AV_LOG_ERROR
, "Unknown DTS sample rate for HD\n");
181 return AVERROR_INVALIDDATA
;
184 period
= ctx
->dtshd_rate
* (blocks
<< 5) / sample_rate
;
185 subtype
= spdif_dts4_subtype(period
);
188 av_log(s
, AV_LOG_ERROR
, "Specified HD rate of %d Hz would require an "
189 "impossible repetition period of %d for the current DTS stream"
190 " (blocks = %d, sample rate = %d)\n", ctx
->dtshd_rate
, period
,
191 blocks
<< 5, sample_rate
);
192 return AVERROR(EINVAL
);
195 /* set pkt_offset and DTS IV subtype according to the requested output
197 ctx
->pkt_offset
= period
* 4;
198 ctx
->data_type
= IEC61937_DTSHD
| subtype
<< 8;
200 /* If the bitrate is too high for transmitting at the selected
201 * repetition period setting, strip DTS-HD until a good amount
202 * of consecutive non-overflowing HD frames have been observed.
203 * This generally only happens if the caller is cramming a Master
204 * Audio stream into 192kHz IEC 60958 (which may or may not fit). */
205 if (sizeof(dtshd_start_code
) + 2 + pkt_size
206 > ctx
->pkt_offset
- BURST_HEADER_SIZE
&& core_size
) {
207 if (!ctx
->dtshd_skip
)
208 av_log(s
, AV_LOG_WARNING
, "DTS-HD bitrate too high, "
209 "temporarily sending core only\n");
210 if (ctx
->dtshd_fallback
> 0)
211 ctx
->dtshd_skip
= sample_rate
* ctx
->dtshd_fallback
/ (blocks
<< 5);
213 /* skip permanently (dtshd_fallback == -1) or just once
214 * (dtshd_fallback == 0) */
217 if (ctx
->dtshd_skip
&& core_size
) {
218 pkt_size
= core_size
;
219 if (ctx
->dtshd_fallback
>= 0)
223 ctx
->out_bytes
= sizeof(dtshd_start_code
) + 2 + pkt_size
;
225 /* Align so that (length_code & 0xf) == 0x8. This is reportedly needed
226 * with some receivers, but the exact requirement is unconfirmed. */
227 ctx
->length_code
= FFALIGN(ctx
->out_bytes
+ 0x8, 0x10) - 0x8;
229 av_fast_malloc(&ctx
->hd_buf
, &ctx
->hd_buf_size
, ctx
->out_bytes
);
231 return AVERROR(ENOMEM
);
233 ctx
->out_buf
= ctx
->hd_buf
;
235 memcpy(ctx
->hd_buf
, dtshd_start_code
, sizeof(dtshd_start_code
));
236 AV_WB16(ctx
->hd_buf
+ sizeof(dtshd_start_code
), pkt_size
);
237 memcpy(ctx
->hd_buf
+ sizeof(dtshd_start_code
) + 2, pkt
->data
, pkt_size
);
242 static int spdif_header_dts(AVFormatContext
*s
, AVPacket
*pkt
)
244 IEC61937Context
*ctx
= s
->priv_data
;
245 uint32_t syncword_dts
= AV_RB32(pkt
->data
);
251 return AVERROR_INVALIDDATA
;
253 switch (syncword_dts
) {
254 case DCA_MARKER_RAW_BE
:
255 blocks
= (AV_RB16(pkt
->data
+ 4) >> 2) & 0x7f;
256 core_size
= ((AV_RB24(pkt
->data
+ 5) >> 4) & 0x3fff) + 1;
257 sample_rate
= avpriv_dca_sample_rates
[(pkt
->data
[8] >> 2) & 0x0f];
259 case DCA_MARKER_RAW_LE
:
260 blocks
= (AV_RL16(pkt
->data
+ 4) >> 2) & 0x7f;
261 ctx
->extra_bswap
= 1;
263 case DCA_MARKER_14B_BE
:
265 (((pkt
->data
[5] & 0x07) << 4) | ((pkt
->data
[6] & 0x3f) >> 2));
267 case DCA_MARKER_14B_LE
:
269 (((pkt
->data
[4] & 0x07) << 4) | ((pkt
->data
[7] & 0x3f) >> 2));
270 ctx
->extra_bswap
= 1;
273 /* We only handle HD frames that are paired with core. However,
274 sometimes DTS-HD streams with core have a stray HD frame without
275 core in the beginning of the stream. */
276 av_log(s
, AV_LOG_ERROR
, "stray DTS-HD frame\n");
277 return AVERROR_INVALIDDATA
;
279 av_log(s
, AV_LOG_ERROR
, "bad DTS syncword 0x%"PRIx32
"\n", syncword_dts
);
280 return AVERROR_INVALIDDATA
;
285 /* DTS type IV output requested */
286 return spdif_header_dts4(s
, pkt
, core_size
, sample_rate
, blocks
);
289 case 512 >> 5: ctx
->data_type
= IEC61937_DTS1
; break;
290 case 1024 >> 5: ctx
->data_type
= IEC61937_DTS2
; break;
291 case 2048 >> 5: ctx
->data_type
= IEC61937_DTS3
; break;
293 av_log(s
, AV_LOG_ERROR
, "%i samples in DTS frame not supported\n",
295 return AVERROR(ENOSYS
);
298 /* discard extraneous data by default */
299 if (core_size
&& core_size
< pkt
->size
) {
300 ctx
->out_bytes
= core_size
;
301 ctx
->length_code
= core_size
<< 3;
304 ctx
->pkt_offset
= blocks
<< 7;
306 if (ctx
->out_bytes
== ctx
->pkt_offset
) {
307 /* The DTS stream fits exactly into the output stream, so skip the
308 * preamble as it would not fit in there. This is the case for dts
309 * discs and dts-in-wav. */
310 ctx
->use_preamble
= 0;
311 } else if (ctx
->out_bytes
> ctx
->pkt_offset
- BURST_HEADER_SIZE
) {
312 avpriv_request_sample(s
, "Unrecognized large DTS frame");
313 /* This will fail with a "bitrate too high" in the caller */
319 static const enum IEC61937DataType mpeg_data_type
[2][3] = {
320 // LAYER1 LAYER2 LAYER3
321 { IEC61937_MPEG2_LAYER1_LSF
, IEC61937_MPEG2_LAYER2_LSF
, IEC61937_MPEG2_LAYER3_LSF
},//MPEG2 LSF
322 { IEC61937_MPEG1_LAYER1
, IEC61937_MPEG1_LAYER23
, IEC61937_MPEG1_LAYER23
}, //MPEG1
325 static int spdif_header_mpeg(AVFormatContext
*s
, AVPacket
*pkt
)
327 IEC61937Context
*ctx
= s
->priv_data
;
328 int version
= (pkt
->data
[1] >> 3) & 3;
329 int layer
= 3 - ((pkt
->data
[1] >> 1) & 3);
330 int extension
= pkt
->data
[2] & 1;
332 if (layer
== 3 || version
== 1) {
333 av_log(s
, AV_LOG_ERROR
, "Wrong MPEG file format\n");
334 return AVERROR_INVALIDDATA
;
336 av_log(s
, AV_LOG_DEBUG
, "version: %i layer: %i extension: %i\n", version
, layer
, extension
);
337 if (version
== 2 && extension
) {
338 ctx
->data_type
= IEC61937_MPEG2_EXT
;
339 ctx
->pkt_offset
= 4608;
341 ctx
->data_type
= mpeg_data_type
[version
& 1][layer
];
342 ctx
->pkt_offset
= spdif_mpeg_pkt_offset
[version
& 1][layer
];
344 // TODO Data type dependent info (normal/karaoke, dynamic range control)
348 static int spdif_header_aac(AVFormatContext
*s
, AVPacket
*pkt
)
350 IEC61937Context
*ctx
= s
->priv_data
;
351 AACADTSHeaderInfo hdr
;
355 init_get_bits(&gbc
, pkt
->data
, AAC_ADTS_HEADER_SIZE
* 8);
356 ret
= avpriv_aac_parse_header(&gbc
, &hdr
);
358 av_log(s
, AV_LOG_ERROR
, "Wrong AAC file format\n");
359 return AVERROR_INVALIDDATA
;
362 ctx
->pkt_offset
= hdr
.samples
<< 2;
363 switch (hdr
.num_aac_frames
) {
365 ctx
->data_type
= IEC61937_MPEG2_AAC
;
368 ctx
->data_type
= IEC61937_MPEG2_AAC_LSF_2048
;
371 ctx
->data_type
= IEC61937_MPEG2_AAC_LSF_4096
;
374 av_log(s
, AV_LOG_ERROR
,
375 "%"PRIu32
" samples in AAC frame not supported\n", hdr
.samples
);
376 return AVERROR(EINVAL
);
378 //TODO Data type dependent info (LC profile/SBR)
384 * It seems Dolby TrueHD frames have to be encapsulated in MAT frames before
385 * they can be encapsulated in IEC 61937.
386 * Here we encapsulate 24 TrueHD frames in a single MAT frame, padding them
387 * to achieve constant rate.
388 * The actual format of a MAT frame is unknown, but the below seems to work.
389 * However, it seems it is not actually necessary for the 24 TrueHD frames to
390 * be in an exact alignment with the MAT frame.
392 #define MAT_FRAME_SIZE 61424
393 #define TRUEHD_FRAME_OFFSET 2560
394 #define MAT_MIDDLE_CODE_OFFSET -4
396 static int spdif_header_truehd(AVFormatContext
*s
, AVPacket
*pkt
)
398 IEC61937Context
*ctx
= s
->priv_data
;
399 int mat_code_length
= 0;
400 static const char mat_end_code
[16] = { 0xC3, 0xC2, 0xC0, 0xC4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x97, 0x11 };
402 if (!ctx
->hd_buf_count
) {
403 static const char mat_start_code
[20] = { 0x07, 0x9E, 0x00, 0x03, 0x84, 0x01, 0x01, 0x01, 0x80, 0x00, 0x56, 0xA5, 0x3B, 0xF4, 0x81, 0x83, 0x49, 0x80, 0x77, 0xE0 };
404 mat_code_length
= sizeof(mat_start_code
) + BURST_HEADER_SIZE
;
405 memcpy(ctx
->hd_buf
, mat_start_code
, sizeof(mat_start_code
));
407 } else if (ctx
->hd_buf_count
== 12) {
408 static const char mat_middle_code
[12] = { 0xC3, 0xC1, 0x42, 0x49, 0x3B, 0xFA, 0x82, 0x83, 0x49, 0x80, 0x77, 0xE0 };
409 mat_code_length
= sizeof(mat_middle_code
) + MAT_MIDDLE_CODE_OFFSET
;
410 memcpy(&ctx
->hd_buf
[12 * TRUEHD_FRAME_OFFSET
- BURST_HEADER_SIZE
+ MAT_MIDDLE_CODE_OFFSET
],
411 mat_middle_code
, sizeof(mat_middle_code
));
414 if (pkt
->size
> TRUEHD_FRAME_OFFSET
- mat_code_length
) {
415 /* if such frames exist, we'd need some more complex logic to
416 * distribute the TrueHD frames in the MAT frame */
417 avpriv_request_sample(s
, "Too large TrueHD frame of %d bytes",
419 return AVERROR_PATCHWELCOME
;
422 memcpy(&ctx
->hd_buf
[ctx
->hd_buf_count
* TRUEHD_FRAME_OFFSET
- BURST_HEADER_SIZE
+ mat_code_length
],
423 pkt
->data
, pkt
->size
);
424 memset(&ctx
->hd_buf
[ctx
->hd_buf_count
* TRUEHD_FRAME_OFFSET
- BURST_HEADER_SIZE
+ mat_code_length
+ pkt
->size
],
425 0, TRUEHD_FRAME_OFFSET
- pkt
->size
- mat_code_length
);
427 if (++ctx
->hd_buf_count
< 24){
431 memcpy(&ctx
->hd_buf
[MAT_FRAME_SIZE
- sizeof(mat_end_code
)], mat_end_code
, sizeof(mat_end_code
));
432 ctx
->hd_buf_count
= 0;
434 ctx
->data_type
= IEC61937_TRUEHD
;
435 ctx
->pkt_offset
= 61440;
436 ctx
->out_buf
= ctx
->hd_buf
;
437 ctx
->out_bytes
= MAT_FRAME_SIZE
;
438 ctx
->length_code
= MAT_FRAME_SIZE
;
442 static int spdif_write_header(AVFormatContext
*s
)
444 IEC61937Context
*ctx
= s
->priv_data
;
446 switch (s
->streams
[0]->codec
->codec_id
) {
447 case AV_CODEC_ID_AC3
:
448 ctx
->header_info
= spdif_header_ac3
;
450 case AV_CODEC_ID_EAC3
:
451 ctx
->header_info
= spdif_header_eac3
;
453 case AV_CODEC_ID_MP1
:
454 case AV_CODEC_ID_MP2
:
455 case AV_CODEC_ID_MP3
:
456 ctx
->header_info
= spdif_header_mpeg
;
458 case AV_CODEC_ID_DTS
:
459 ctx
->header_info
= spdif_header_dts
;
461 case AV_CODEC_ID_AAC
:
462 ctx
->header_info
= spdif_header_aac
;
464 case AV_CODEC_ID_TRUEHD
:
465 ctx
->header_info
= spdif_header_truehd
;
466 ctx
->hd_buf
= av_malloc(MAT_FRAME_SIZE
);
468 return AVERROR(ENOMEM
);
471 av_log(s
, AV_LOG_ERROR
, "codec not supported\n");
472 return AVERROR_PATCHWELCOME
;
477 static int spdif_write_trailer(AVFormatContext
*s
)
479 IEC61937Context
*ctx
= s
->priv_data
;
480 av_freep(&ctx
->buffer
);
481 av_freep(&ctx
->hd_buf
);
485 static av_always_inline
void spdif_put_16(IEC61937Context
*ctx
,
486 AVIOContext
*pb
, unsigned int val
)
488 if (ctx
->spdif_flags
& SPDIF_FLAG_BIGENDIAN
)
494 static int spdif_write_packet(struct AVFormatContext
*s
, AVPacket
*pkt
)
496 IEC61937Context
*ctx
= s
->priv_data
;
499 ctx
->out_buf
= pkt
->data
;
500 ctx
->out_bytes
= pkt
->size
;
501 ctx
->length_code
= FFALIGN(pkt
->size
, 2) << 3;
502 ctx
->use_preamble
= 1;
503 ctx
->extra_bswap
= 0;
505 ret
= ctx
->header_info(s
, pkt
);
508 if (!ctx
->pkt_offset
)
511 padding
= (ctx
->pkt_offset
- ctx
->use_preamble
* BURST_HEADER_SIZE
- ctx
->out_bytes
) & ~1;
513 av_log(s
, AV_LOG_ERROR
, "bitrate is too high\n");
514 return AVERROR(EINVAL
);
517 if (ctx
->use_preamble
) {
518 spdif_put_16(ctx
, s
->pb
, SYNCWORD1
); //Pa
519 spdif_put_16(ctx
, s
->pb
, SYNCWORD2
); //Pb
520 spdif_put_16(ctx
, s
->pb
, ctx
->data_type
); //Pc
521 spdif_put_16(ctx
, s
->pb
, ctx
->length_code
);//Pd
524 if (ctx
->extra_bswap
^ (ctx
->spdif_flags
& SPDIF_FLAG_BIGENDIAN
)) {
525 avio_write(s
->pb
, ctx
->out_buf
, ctx
->out_bytes
& ~1);
527 av_fast_malloc(&ctx
->buffer
, &ctx
->buffer_size
, ctx
->out_bytes
+ FF_INPUT_BUFFER_PADDING_SIZE
);
529 return AVERROR(ENOMEM
);
530 ff_spdif_bswap_buf16((uint16_t *)ctx
->buffer
, (uint16_t *)ctx
->out_buf
, ctx
->out_bytes
>> 1);
531 avio_write(s
->pb
, ctx
->buffer
, ctx
->out_bytes
& ~1);
534 /* a final lone byte has to be MSB aligned */
535 if (ctx
->out_bytes
& 1)
536 spdif_put_16(ctx
, s
->pb
, ctx
->out_buf
[ctx
->out_bytes
- 1] << 8);
538 ffio_fill(s
->pb
, 0, padding
);
540 av_log(s
, AV_LOG_DEBUG
, "type=%x len=%i pkt_offset=%i\n",
541 ctx
->data_type
, ctx
->out_bytes
, ctx
->pkt_offset
);
546 AVOutputFormat ff_spdif_muxer
= {
548 .long_name
= NULL_IF_CONFIG_SMALL("IEC 61937 (used on S/PDIF - IEC958)"),
549 .extensions
= "spdif",
550 .priv_data_size
= sizeof(IEC61937Context
),
551 .audio_codec
= AV_CODEC_ID_AC3
,
552 .video_codec
= AV_CODEC_ID_NONE
,
553 .write_header
= spdif_write_header
,
554 .write_packet
= spdif_write_packet
,
555 .write_trailer
= spdif_write_trailer
,
556 .flags
= AVFMT_NOTIMESTAMPS
,
557 .priv_class
= &spdif_class
,