spdifenc.c 20.1 KB
Newer Older
1
/*
2
 * IEC 61937 muxer
3
 * Copyright (c) 2009 Bartlomiej Wolowiec
4 5
 * Copyright (c) 2010 Anssi Hannula
 * Copyright (c) 2010 Carl Eugen Hoyos
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
 *
 * 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
 */

/**
25
 * @file
26 27
 * IEC-61937 encapsulation of various formats, used by S/PDIF
 * @author Bartlomiej Wolowiec
28 29
 * @author Anssi Hannula
 * @author Carl Eugen Hoyos
30 31 32 33
 */

/*
 * Terminology used in specification:
34
 * data-burst - IEC61937 frame, contains header and encapsuled frame
35
 * burst-preamble - IEC61937 frame header, contains 16-bit words named Pa, Pb, Pc and Pd
36 37 38 39 40 41 42
 * burst-payload - encapsuled frame
 * Pa, Pb - syncword - 0xF872, 0x4E1F
 * Pc - burst-info, contains data-type (bits 0-6), error flag (bit 7), data-type-dependent info (bits 8-12)
 *      and bitstream number (bits 13-15)
 * data-type - determines type of encapsuled frames
 * 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 45 46
 *      dependent from data-type (spaces between packets are filled by zeros)
 */

47 48
#include <inttypes.h>

49
#include "avformat.h"
50
#include "avio_internal.h"
51
#include "spdif.h"
52 53
#include "libavcodec/ac3.h"
#include "libavcodec/dca.h"
54
#include "libavcodec/dca_syncwords.h"
55
#include "libavcodec/aacadtsdec.h"
56
#include "libavutil/opt.h"
57

58
typedef struct IEC61937Context {
59
    const AVClass *av_class;
60
    enum IEC61937DataType data_type;///< burst info - reference to type of payload of the data-burst
61
    int length_code;                ///< length code in bits or bytes, depending on data type
62 63 64 65
    int pkt_offset;                 ///< data burst repetition period in bytes
    uint8_t *buffer;                ///< allocated buffer, used for swap bytes
    int buffer_size;                ///< size of allocated buffer

66 67 68
    uint8_t *out_buf;               ///< pointer to the outgoing data before byte-swapping
    int out_bytes;                  ///< amount of outgoing bytes

69
    int use_preamble;               ///< preamble enabled (disabled for exactly pre-padded DTS)
70 71
    int extra_bswap;                ///< extra bswap for payload (for LE DTS => standard BE DTS)

72 73 74 75 76
    uint8_t *hd_buf;                ///< allocated buffer to concatenate hd audio frames
    int hd_buf_size;                ///< size of the hd audio buffer
    int hd_buf_count;               ///< number of frames in the hd audio buffer
    int hd_buf_filled;              ///< amount of bytes in the hd audio buffer

77 78 79 80 81
    int dtshd_skip;                 ///< counter used for skipping DTS-HD frames

    /* AVOptions: */
    int dtshd_rate;
    int dtshd_fallback;
82 83
#define SPDIF_FLAG_BIGENDIAN    0x01
    int spdif_flags;
84

85
    /// function, which generates codec dependent header information.
86
    /// Sets data_type and pkt_offset, and length_code, out_bytes, out_buf if necessary
87
    int (*header_info) (AVFormatContext *s, AVPacket *pkt);
88
} IEC61937Context;
89

90
static const AVOption options[] = {
91
{ "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" },
92
{ "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" },
93 94
{ "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 },
{ "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 },
95 96 97
{ NULL },
};

98
static const AVClass spdif_class = {
99 100 101 102 103
    .class_name     = "spdif",
    .item_name      = av_default_item_name,
    .option         = options,
    .version        = LIBAVUTIL_VERSION_INT,
};
104 105 106

static int spdif_header_ac3(AVFormatContext *s, AVPacket *pkt)
{
107
    IEC61937Context *ctx = s->priv_data;
108
    int bitstream_mode = pkt->data[5] & 0x7;
109

110
    ctx->data_type  = IEC61937_AC3 | (bitstream_mode << 8);
111 112 113 114
    ctx->pkt_offset = AC3_FRAME_SIZE << 2;
    return 0;
}

115 116
static int spdif_header_eac3(AVFormatContext *s, AVPacket *pkt)
{
117
    IEC61937Context *ctx = s->priv_data;
118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134
    static const uint8_t eac3_repeat[4] = {6, 3, 2, 1};
    int repeat = 1;

    if ((pkt->data[4] & 0xc0) != 0xc0) /* fscod */
        repeat = eac3_repeat[(pkt->data[4] & 0x30) >> 4]; /* numblkscod */

    ctx->hd_buf = av_fast_realloc(ctx->hd_buf, &ctx->hd_buf_size, ctx->hd_buf_filled + pkt->size);
    if (!ctx->hd_buf)
        return AVERROR(ENOMEM);

    memcpy(&ctx->hd_buf[ctx->hd_buf_filled], pkt->data, pkt->size);

    ctx->hd_buf_filled += pkt->size;
    if (++ctx->hd_buf_count < repeat){
        ctx->pkt_offset = 0;
        return 0;
    }
135
    ctx->data_type   = IEC61937_EAC3;
136 137 138 139 140 141 142 143 144 145
    ctx->pkt_offset  = 24576;
    ctx->out_buf     = ctx->hd_buf;
    ctx->out_bytes   = ctx->hd_buf_filled;
    ctx->length_code = ctx->hd_buf_filled;

    ctx->hd_buf_count  = 0;
    ctx->hd_buf_filled = 0;
    return 0;
}

146 147 148 149
/*
 * DTS type IV (DTS-HD) can be transmitted with various frame repetition
 * periods; longer repetition periods allow for longer packets and therefore
 * higher bitrate. Longer repetition periods mean that the constant bitrate of
150
 * the output IEC 61937 stream is higher.
151 152 153 154 155
 * The repetition period is measured in IEC 60958 frames (4 bytes).
 */
static int spdif_dts4_subtype(int period)
{
    switch (period) {
156 157 158 159 160 161
    case 512:   return 0x0;
    case 1024:  return 0x1;
    case 2048:  return 0x2;
    case 4096:  return 0x3;
    case 8192:  return 0x4;
    case 16384: return 0x5;
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
    }
    return -1;
}

static int spdif_header_dts4(AVFormatContext *s, AVPacket *pkt, int core_size,
                             int sample_rate, int blocks)
{
    IEC61937Context *ctx = s->priv_data;
    static const char dtshd_start_code[10] = { 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfe, 0xfe };
    int pkt_size = pkt->size;
    int period;
    int subtype;

    if (!core_size) {
        av_log(s, AV_LOG_ERROR, "HD mode not supported for this format\n");
        return AVERROR(EINVAL);
    }

    if (!sample_rate) {
        av_log(s, AV_LOG_ERROR, "Unknown DTS sample rate for HD\n");
        return AVERROR_INVALIDDATA;
    }

    period = ctx->dtshd_rate * (blocks << 5) / sample_rate;
    subtype = spdif_dts4_subtype(period);

    if (subtype < 0) {
        av_log(s, AV_LOG_ERROR, "Specified HD rate of %d Hz would require an "
               "impossible repetition period of %d for the current DTS stream"
               " (blocks = %d, sample rate = %d)\n", ctx->dtshd_rate, period,
               blocks << 5, sample_rate);
        return AVERROR(EINVAL);
    }

    /* set pkt_offset and DTS IV subtype according to the requested output
     * rate */
    ctx->pkt_offset = period * 4;
    ctx->data_type = IEC61937_DTSHD | subtype << 8;

    /* If the bitrate is too high for transmitting at the selected
     * repetition period setting, strip DTS-HD until a good amount
     * of consecutive non-overflowing HD frames have been observed.
     * This generally only happens if the caller is cramming a Master
     * Audio stream into 192kHz IEC 60958 (which may or may not fit). */
    if (sizeof(dtshd_start_code) + 2 + pkt_size
            > ctx->pkt_offset - BURST_HEADER_SIZE && core_size) {
        if (!ctx->dtshd_skip)
            av_log(s, AV_LOG_WARNING, "DTS-HD bitrate too high, "
                                      "temporarily sending core only\n");
        if (ctx->dtshd_fallback > 0)
            ctx->dtshd_skip = sample_rate * ctx->dtshd_fallback / (blocks << 5);
        else
214 215
            /* skip permanently (dtshd_fallback == -1) or just once
             * (dtshd_fallback == 0) */
216 217 218 219 220 221 222 223 224
            ctx->dtshd_skip = 1;
    }
    if (ctx->dtshd_skip && core_size) {
        pkt_size = core_size;
        if (ctx->dtshd_fallback >= 0)
            --ctx->dtshd_skip;
    }

    ctx->out_bytes   = sizeof(dtshd_start_code) + 2 + pkt_size;
225 226 227 228

    /* Align so that (length_code & 0xf) == 0x8. This is reportedly needed
     * with some receivers, but the exact requirement is unconfirmed. */
    ctx->length_code = FFALIGN(ctx->out_bytes + 0x8, 0x10) - 0x8;
229

230
    av_fast_malloc(&ctx->hd_buf, &ctx->hd_buf_size, ctx->out_bytes);
231 232 233 234 235 236 237 238 239 240 241 242
    if (!ctx->hd_buf)
        return AVERROR(ENOMEM);

    ctx->out_buf = ctx->hd_buf;

    memcpy(ctx->hd_buf, dtshd_start_code, sizeof(dtshd_start_code));
    AV_WB16(ctx->hd_buf + sizeof(dtshd_start_code), pkt_size);
    memcpy(ctx->hd_buf + sizeof(dtshd_start_code) + 2, pkt->data, pkt_size);

    return 0;
}

243 244
static int spdif_header_dts(AVFormatContext *s, AVPacket *pkt)
{
245
    IEC61937Context *ctx = s->priv_data;
246 247
    uint32_t syncword_dts = AV_RB32(pkt->data);
    int blocks;
248 249 250 251 252
    int sample_rate = 0;
    int core_size = 0;

    if (pkt->size < 9)
        return AVERROR_INVALIDDATA;
253 254

    switch (syncword_dts) {
255
    case DCA_SYNCWORD_CORE_BE:
256
        blocks = (AV_RB16(pkt->data + 4) >> 2) & 0x7f;
257
        core_size = ((AV_RB24(pkt->data + 5) >> 4) & 0x3fff) + 1;
258
        sample_rate = avpriv_dca_sample_rates[(pkt->data[8] >> 2) & 0x0f];
259
        break;
260
    case DCA_SYNCWORD_CORE_LE:
261
        blocks = (AV_RL16(pkt->data + 4) >> 2) & 0x7f;
262
        ctx->extra_bswap = 1;
263
        break;
264
    case DCA_SYNCWORD_CORE_14B_BE:
265 266 267
        blocks =
            (((pkt->data[5] & 0x07) << 4) | ((pkt->data[6] & 0x3f) >> 2));
        break;
268
    case DCA_SYNCWORD_CORE_14B_LE:
269 270
        blocks =
            (((pkt->data[4] & 0x07) << 4) | ((pkt->data[7] & 0x3f) >> 2));
271
        ctx->extra_bswap = 1;
272
        break;
273
    case DCA_SYNCWORD_SUBSTREAM:
274 275 276 277 278
        /* We only handle HD frames that are paired with core. However,
           sometimes DTS-HD streams with core have a stray HD frame without
           core in the beginning of the stream. */
        av_log(s, AV_LOG_ERROR, "stray DTS-HD frame\n");
        return AVERROR_INVALIDDATA;
279
    default:
280
        av_log(s, AV_LOG_ERROR, "bad DTS syncword 0x%"PRIx32"\n", syncword_dts);
281
        return AVERROR_INVALIDDATA;
282 283
    }
    blocks++;
284 285 286 287 288

    if (ctx->dtshd_rate)
        /* DTS type IV output requested */
        return spdif_header_dts4(s, pkt, core_size, sample_rate, blocks);

289
    switch (blocks) {
290 291 292
    case  512 >> 5: ctx->data_type = IEC61937_DTS1; break;
    case 1024 >> 5: ctx->data_type = IEC61937_DTS2; break;
    case 2048 >> 5: ctx->data_type = IEC61937_DTS3; break;
293 294 295
    default:
        av_log(s, AV_LOG_ERROR, "%i samples in DTS frame not supported\n",
               blocks << 5);
296
        return AVERROR(ENOSYS);
297
    }
298 299 300 301 302 303 304

    /* discard extraneous data by default */
    if (core_size && core_size < pkt->size) {
        ctx->out_bytes = core_size;
        ctx->length_code = core_size << 3;
    }

305 306
    ctx->pkt_offset = blocks << 7;

307 308 309 310 311
    if (ctx->out_bytes == ctx->pkt_offset) {
        /* The DTS stream fits exactly into the output stream, so skip the
         * preamble as it would not fit in there. This is the case for dts
         * discs and dts-in-wav. */
        ctx->use_preamble = 0;
312
    } else if (ctx->out_bytes > ctx->pkt_offset - BURST_HEADER_SIZE) {
313
        avpriv_request_sample(s, "Unrecognized large DTS frame");
314
        /* This will fail with a "bitrate too high" in the caller */
315 316
    }

317 318 319
    return 0;
}

320
static const enum IEC61937DataType mpeg_data_type[2][3] = {
321
    //     LAYER1                      LAYER2                  LAYER3
322 323
    { IEC61937_MPEG2_LAYER1_LSF, IEC61937_MPEG2_LAYER2_LSF, IEC61937_MPEG2_LAYER3_LSF }, // MPEG-2 LSF
    { IEC61937_MPEG1_LAYER1,     IEC61937_MPEG1_LAYER23,    IEC61937_MPEG1_LAYER23 },    // MPEG-1
324 325 326 327
};

static int spdif_header_mpeg(AVFormatContext *s, AVPacket *pkt)
{
328
    IEC61937Context *ctx = s->priv_data;
329 330 331 332 333 334
    int version =      (pkt->data[1] >> 3) & 3;
    int layer   = 3 - ((pkt->data[1] >> 1) & 3);
    int extension = pkt->data[2] & 1;

    if (layer == 3 || version == 1) {
        av_log(s, AV_LOG_ERROR, "Wrong MPEG file format\n");
335
        return AVERROR_INVALIDDATA;
336 337 338
    }
    av_log(s, AV_LOG_DEBUG, "version: %i layer: %i extension: %i\n", version, layer, extension);
    if (version == 2 && extension) {
339
        ctx->data_type  = IEC61937_MPEG2_EXT;
340 341 342
        ctx->pkt_offset = 4608;
    } else {
        ctx->data_type  = mpeg_data_type [version & 1][layer];
343
        ctx->pkt_offset = spdif_mpeg_pkt_offset[version & 1][layer];
344
    }
Diego Biurrun's avatar
Diego Biurrun committed
345
    // TODO Data type dependent info (normal/karaoke, dynamic range control)
346 347 348 349 350
    return 0;
}

static int spdif_header_aac(AVFormatContext *s, AVPacket *pkt)
{
351
    IEC61937Context *ctx = s->priv_data;
352 353 354 355 356
    AACADTSHeaderInfo hdr;
    GetBitContext gbc;
    int ret;

    init_get_bits(&gbc, pkt->data, AAC_ADTS_HEADER_SIZE * 8);
357
    ret = avpriv_aac_parse_header(&gbc, &hdr);
358 359
    if (ret < 0) {
        av_log(s, AV_LOG_ERROR, "Wrong AAC file format\n");
360
        return AVERROR_INVALIDDATA;
361 362 363 364 365
    }

    ctx->pkt_offset = hdr.samples << 2;
    switch (hdr.num_aac_frames) {
    case 1:
366
        ctx->data_type = IEC61937_MPEG2_AAC;
367 368
        break;
    case 2:
369
        ctx->data_type = IEC61937_MPEG2_AAC_LSF_2048;
370 371
        break;
    case 4:
372
        ctx->data_type = IEC61937_MPEG2_AAC_LSF_4096;
373 374
        break;
    default:
375 376
        av_log(s, AV_LOG_ERROR,
               "%"PRIu32" samples in AAC frame not supported\n", hdr.samples);
377
        return AVERROR(EINVAL);
378 379 380 381 382
    }
    //TODO Data type dependent info (LC profile/SBR)
    return 0;
}

383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398

/*
 * It seems Dolby TrueHD frames have to be encapsulated in MAT frames before
 * they can be encapsulated in IEC 61937.
 * Here we encapsulate 24 TrueHD frames in a single MAT frame, padding them
 * to achieve constant rate.
 * The actual format of a MAT frame is unknown, but the below seems to work.
 * However, it seems it is not actually necessary for the 24 TrueHD frames to
 * be in an exact alignment with the MAT frame.
 */
#define MAT_FRAME_SIZE          61424
#define TRUEHD_FRAME_OFFSET     2560
#define MAT_MIDDLE_CODE_OFFSET  -4

static int spdif_header_truehd(AVFormatContext *s, AVPacket *pkt)
{
399
    IEC61937Context *ctx = s->priv_data;
400
    int mat_code_length = 0;
401
    static const char mat_end_code[16] = { 0xC3, 0xC2, 0xC0, 0xC4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x97, 0x11 };
402 403

    if (!ctx->hd_buf_count) {
404
        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 };
405 406 407 408
        mat_code_length = sizeof(mat_start_code) + BURST_HEADER_SIZE;
        memcpy(ctx->hd_buf, mat_start_code, sizeof(mat_start_code));

    } else if (ctx->hd_buf_count == 12) {
409
        static const char mat_middle_code[12] = { 0xC3, 0xC1, 0x42, 0x49, 0x3B, 0xFA, 0x82, 0x83, 0x49, 0x80, 0x77, 0xE0 };
410 411 412 413 414 415 416 417
        mat_code_length = sizeof(mat_middle_code) + MAT_MIDDLE_CODE_OFFSET;
        memcpy(&ctx->hd_buf[12 * TRUEHD_FRAME_OFFSET - BURST_HEADER_SIZE + MAT_MIDDLE_CODE_OFFSET],
               mat_middle_code, sizeof(mat_middle_code));
    }

    if (pkt->size > TRUEHD_FRAME_OFFSET - mat_code_length) {
        /* if such frames exist, we'd need some more complex logic to
         * distribute the TrueHD frames in the MAT frame */
418 419
        avpriv_request_sample(s, "Too large TrueHD frame of %d bytes",
                              pkt->size);
420
        return AVERROR_PATCHWELCOME;
421 422 423 424 425 426 427 428 429 430 431 432 433 434
    }

    memcpy(&ctx->hd_buf[ctx->hd_buf_count * TRUEHD_FRAME_OFFSET - BURST_HEADER_SIZE + mat_code_length],
           pkt->data, pkt->size);
    memset(&ctx->hd_buf[ctx->hd_buf_count * TRUEHD_FRAME_OFFSET - BURST_HEADER_SIZE + mat_code_length + pkt->size],
           0, TRUEHD_FRAME_OFFSET - pkt->size - mat_code_length);

    if (++ctx->hd_buf_count < 24){
        ctx->pkt_offset = 0;
        return 0;
    }
    memcpy(&ctx->hd_buf[MAT_FRAME_SIZE - sizeof(mat_end_code)], mat_end_code, sizeof(mat_end_code));
    ctx->hd_buf_count = 0;

435
    ctx->data_type   = IEC61937_TRUEHD;
436 437 438 439 440 441 442
    ctx->pkt_offset  = 61440;
    ctx->out_buf     = ctx->hd_buf;
    ctx->out_bytes   = MAT_FRAME_SIZE;
    ctx->length_code = MAT_FRAME_SIZE;
    return 0;
}

443 444
static int spdif_write_header(AVFormatContext *s)
{
445
    IEC61937Context *ctx = s->priv_data;
446

447
    switch (s->streams[0]->codecpar->codec_id) {
448
    case AV_CODEC_ID_AC3:
449 450
        ctx->header_info = spdif_header_ac3;
        break;
451
    case AV_CODEC_ID_EAC3:
452 453
        ctx->header_info = spdif_header_eac3;
        break;
454 455 456
    case AV_CODEC_ID_MP1:
    case AV_CODEC_ID_MP2:
    case AV_CODEC_ID_MP3:
457 458
        ctx->header_info = spdif_header_mpeg;
        break;
459
    case AV_CODEC_ID_DTS:
460 461
        ctx->header_info = spdif_header_dts;
        break;
462
    case AV_CODEC_ID_AAC:
463 464
        ctx->header_info = spdif_header_aac;
        break;
465
    case AV_CODEC_ID_TRUEHD:
466
    case AV_CODEC_ID_MLP:
467 468 469 470 471
        ctx->header_info = spdif_header_truehd;
        ctx->hd_buf = av_malloc(MAT_FRAME_SIZE);
        if (!ctx->hd_buf)
            return AVERROR(ENOMEM);
        break;
472 473
    default:
        av_log(s, AV_LOG_ERROR, "codec not supported\n");
474
        return AVERROR_PATCHWELCOME;
475 476 477 478 479 480
    }
    return 0;
}

static int spdif_write_trailer(AVFormatContext *s)
{
481
    IEC61937Context *ctx = s->priv_data;
482
    av_freep(&ctx->buffer);
483
    av_freep(&ctx->hd_buf);
484 485 486
    return 0;
}

487
static av_always_inline void spdif_put_16(IEC61937Context *ctx,
488
                                          AVIOContext *pb, unsigned int val)
489 490
{
    if (ctx->spdif_flags & SPDIF_FLAG_BIGENDIAN)
491
        avio_wb16(pb, val);
492
    else
493
        avio_wl16(pb, val);
494 495
}

496 497
static int spdif_write_packet(struct AVFormatContext *s, AVPacket *pkt)
{
498
    IEC61937Context *ctx = s->priv_data;
499 500
    int ret, padding;

501
    ctx->out_buf = pkt->data;
502 503
    ctx->out_bytes = pkt->size;
    ctx->length_code = FFALIGN(pkt->size, 2) << 3;
504
    ctx->use_preamble = 1;
505
    ctx->extra_bswap = 0;
506

507 508
    ret = ctx->header_info(s, pkt);
    if (ret < 0)
509
        return ret;
510 511
    if (!ctx->pkt_offset)
        return 0;
512

513
    padding = (ctx->pkt_offset - ctx->use_preamble * BURST_HEADER_SIZE - ctx->out_bytes) & ~1;
514 515
    if (padding < 0) {
        av_log(s, AV_LOG_ERROR, "bitrate is too high\n");
516
        return AVERROR(EINVAL);
517 518
    }

519
    if (ctx->use_preamble) {
520 521 522 523
        spdif_put_16(ctx, s->pb, SYNCWORD1);       //Pa
        spdif_put_16(ctx, s->pb, SYNCWORD2);       //Pb
        spdif_put_16(ctx, s->pb, ctx->data_type);  //Pc
        spdif_put_16(ctx, s->pb, ctx->length_code);//Pd
524
    }
525

526
    if (ctx->extra_bswap ^ (ctx->spdif_flags & SPDIF_FLAG_BIGENDIAN)) {
527
        avio_write(s->pb, ctx->out_buf, ctx->out_bytes & ~1);
528
    } else {
529
        av_fast_malloc(&ctx->buffer, &ctx->buffer_size, ctx->out_bytes + AV_INPUT_BUFFER_PADDING_SIZE);
530 531 532 533
        if (!ctx->buffer)
            return AVERROR(ENOMEM);
        ff_spdif_bswap_buf16((uint16_t *)ctx->buffer, (uint16_t *)ctx->out_buf, ctx->out_bytes >> 1);
        avio_write(s->pb, ctx->buffer, ctx->out_bytes & ~1);
534
    }
535

536
    /* a final lone byte has to be MSB aligned */
537
    if (ctx->out_bytes & 1)
538
        spdif_put_16(ctx, s->pb, ctx->out_buf[ctx->out_bytes - 1] << 8);
539

540
    ffio_fill(s->pb, 0, padding);
541 542

    av_log(s, AV_LOG_DEBUG, "type=%x len=%i pkt_offset=%i\n",
543
           ctx->data_type, ctx->out_bytes, ctx->pkt_offset);
544 545 546 547

    return 0;
}

548
AVOutputFormat ff_spdif_muxer = {
549 550 551 552
    .name              = "spdif",
    .long_name         = NULL_IF_CONFIG_SMALL("IEC 61937 (used on S/PDIF - IEC958)"),
    .extensions        = "spdif",
    .priv_data_size    = sizeof(IEC61937Context),
553 554
    .audio_codec       = AV_CODEC_ID_AC3,
    .video_codec       = AV_CODEC_ID_NONE,
555 556 557
    .write_header      = spdif_write_header,
    .write_packet      = spdif_write_packet,
    .write_trailer     = spdif_write_trailer,
558
    .flags             = AVFMT_NOTIMESTAMPS,
559
    .priv_class        = &spdif_class,
560
};