FFmpeg: libavcodec/pcm.c Source File

00001 /*
00002  * PCM codecs
00003  * Copyright (c) 2001 Fabrice Bellard
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00027 #include "avcodec.h"
00028 #include "libavutil/common.h" /* for av_reverse */
00029 #include "bytestream.h"
00030 #include "pcm_tablegen.h"
00031 
00032 #define MAX_CHANNELS 64
00033 
00034 static av_cold int pcm_encode_init(AVCodecContext *avctx)
00035 {
00036     avctx->frame_size = 1;
00037     switch(avctx->codec->id) {
00038     case CODEC_ID_PCM_ALAW:
00039         pcm_alaw_tableinit();
00040         break;
00041     case CODEC_ID_PCM_MULAW:
00042         pcm_ulaw_tableinit();
00043         break;
00044     default:
00045         break;
00046     }
00047 
00048     avctx->bits_per_coded_sample = av_get_bits_per_sample(avctx->codec->id);
00049     avctx->block_align = avctx->channels * avctx->bits_per_coded_sample/8;
00050     avctx->coded_frame= avcodec_alloc_frame();
00051     avctx->coded_frame->key_frame= 1;
00052 
00053     return 0;
00054 }
00055 
00056 static av_cold int pcm_encode_close(AVCodecContext *avctx)
00057 {
00058     av_freep(&avctx->coded_frame);
00059 
00060     return 0;
00061 }
00062 
00073 #define ENCODE(type, endian, src, dst, n, shift, offset) \
00074     samples_##type = (const type*) src; \
00075     for(;n>0;n--) { \
00076         register type v = (*samples_##type++ >> shift) + offset; \
00077         bytestream_put_##endian(&dst, v); \
00078     }
00079 
00080 static int pcm_encode_frame(AVCodecContext *avctx,
00081                             unsigned char *frame, int buf_size, void *data)
00082 {
00083     int n, sample_size, v;
00084     const short *samples;
00085     unsigned char *dst;
00086     const uint8_t *srcu8;
00087     const int16_t *samples_int16_t;
00088     const int32_t *samples_int32_t;
00089     const int64_t *samples_int64_t;
00090     const uint16_t *samples_uint16_t;
00091     const uint32_t *samples_uint32_t;
00092 
00093     sample_size = av_get_bits_per_sample(avctx->codec->id)/8;
00094     n = buf_size / sample_size;
00095     samples = data;
00096     dst = frame;
00097 
00098     if (avctx->sample_fmt!=avctx->codec->sample_fmts[0]) {
00099         av_log(avctx, AV_LOG_ERROR, "invalid sample_fmt\n");
00100         return -1;
00101     }
00102 
00103     switch(avctx->codec->id) {
00104     case CODEC_ID_PCM_U32LE:
00105         ENCODE(uint32_t, le32, samples, dst, n, 0, 0x80000000)
00106         break;
00107     case CODEC_ID_PCM_U32BE:
00108         ENCODE(uint32_t, be32, samples, dst, n, 0, 0x80000000)
00109         break;
00110     case CODEC_ID_PCM_S24LE:
00111         ENCODE(int32_t, le24, samples, dst, n, 8, 0)
00112         break;
00113     case CODEC_ID_PCM_S24BE:
00114         ENCODE(int32_t, be24, samples, dst, n, 8, 0)
00115         break;
00116     case CODEC_ID_PCM_U24LE:
00117         ENCODE(uint32_t, le24, samples, dst, n, 8, 0x800000)
00118         break;
00119     case CODEC_ID_PCM_U24BE:
00120         ENCODE(uint32_t, be24, samples, dst, n, 8, 0x800000)
00121         break;
00122     case CODEC_ID_PCM_S24DAUD:
00123         for(;n>0;n--) {
00124             uint32_t tmp = av_reverse[(*samples >> 8) & 0xff] +
00125                            (av_reverse[*samples & 0xff] << 8);
00126             tmp <<= 4; // sync flags would go here
00127             bytestream_put_be24(&dst, tmp);
00128             samples++;
00129         }
00130         break;
00131     case CODEC_ID_PCM_U16LE:
00132         ENCODE(uint16_t, le16, samples, dst, n, 0, 0x8000)
00133         break;
00134     case CODEC_ID_PCM_U16BE:
00135         ENCODE(uint16_t, be16, samples, dst, n, 0, 0x8000)
00136         break;
00137     case CODEC_ID_PCM_S8:
00138         srcu8= data;
00139         for(;n>0;n--) {
00140             v = *srcu8++;
00141             *dst++ = v - 128;
00142         }
00143         break;
00144 #if HAVE_BIGENDIAN
00145     case CODEC_ID_PCM_F64LE:
00146         ENCODE(int64_t, le64, samples, dst, n, 0, 0)
00147         break;
00148     case CODEC_ID_PCM_S32LE:
00149     case CODEC_ID_PCM_F32LE:
00150         ENCODE(int32_t, le32, samples, dst, n, 0, 0)
00151         break;
00152     case CODEC_ID_PCM_S16LE:
00153         ENCODE(int16_t, le16, samples, dst, n, 0, 0)
00154         break;
00155     case CODEC_ID_PCM_F64BE:
00156     case CODEC_ID_PCM_F32BE:
00157     case CODEC_ID_PCM_S32BE:
00158     case CODEC_ID_PCM_S16BE:
00159 #else
00160     case CODEC_ID_PCM_F64BE:
00161         ENCODE(int64_t, be64, samples, dst, n, 0, 0)
00162         break;
00163     case CODEC_ID_PCM_F32BE:
00164     case CODEC_ID_PCM_S32BE:
00165         ENCODE(int32_t, be32, samples, dst, n, 0, 0)
00166         break;
00167     case CODEC_ID_PCM_S16BE:
00168         ENCODE(int16_t, be16, samples, dst, n, 0, 0)
00169         break;
00170     case CODEC_ID_PCM_F64LE:
00171     case CODEC_ID_PCM_F32LE:
00172     case CODEC_ID_PCM_S32LE:
00173     case CODEC_ID_PCM_S16LE:
00174 #endif /* HAVE_BIGENDIAN */
00175     case CODEC_ID_PCM_U8:
00176         memcpy(dst, samples, n*sample_size);
00177         dst += n*sample_size;
00178         break;
00179     case CODEC_ID_PCM_ZORK:
00180         for(;n>0;n--) {
00181             v= *samples++ >> 8;
00182             if(v<0)   v = -v;
00183             else      v+= 128;
00184             *dst++ = v;
00185         }
00186         break;
00187     case CODEC_ID_PCM_ALAW:
00188         for(;n>0;n--) {
00189             v = *samples++;
00190             *dst++ = linear_to_alaw[(v + 32768) >> 2];
00191         }
00192         break;
00193     case CODEC_ID_PCM_MULAW:
00194         for(;n>0;n--) {
00195             v = *samples++;
00196             *dst++ = linear_to_ulaw[(v + 32768) >> 2];
00197         }
00198         break;
00199     default:
00200         return -1;
00201     }
00202     //avctx->frame_size = (dst - frame) / (sample_size * avctx->channels);
00203 
00204     return dst - frame;
00205 }
00206 
00207 typedef struct PCMDecode {
00208     short table[256];
00209 } PCMDecode;
00210 
00211 static av_cold int pcm_decode_init(AVCodecContext * avctx)
00212 {
00213     PCMDecode *s = avctx->priv_data;
00214     int i;
00215 
00216     switch(avctx->codec->id) {
00217     case CODEC_ID_PCM_ALAW:
00218         for(i=0;i<256;i++)
00219             s->table[i] = alaw2linear(i);
00220         break;
00221     case CODEC_ID_PCM_MULAW:
00222         for(i=0;i<256;i++)
00223             s->table[i] = ulaw2linear(i);
00224         break;
00225     default:
00226         break;
00227     }
00228 
00229     avctx->sample_fmt = avctx->codec->sample_fmts[0];
00230 
00231     if (avctx->sample_fmt == AV_SAMPLE_FMT_S32)
00232         avctx->bits_per_raw_sample = av_get_bits_per_sample(avctx->codec->id);
00233 
00234     return 0;
00235 }
00236 
00247 #define DECODE(type, endian, src, dst, n, shift, offset) \
00248     dst_##type = (type*)dst; \
00249     for(;n>0;n--) { \
00250         register type v = bytestream_get_##endian(&src); \
00251         *dst_##type++ = (v - offset) << shift; \
00252     } \
00253     dst = (short*)dst_##type;
00254 
00255 static int pcm_decode_frame(AVCodecContext *avctx,
00256                             void *data, int *data_size,
00257                             AVPacket *avpkt)
00258 {
00259     const uint8_t *buf = avpkt->data;
00260     int buf_size = avpkt->size;
00261     PCMDecode *s = avctx->priv_data;
00262     int sample_size, c, n, i;
00263     short *samples;
00264     const uint8_t *src, *src8, *src2[MAX_CHANNELS];
00265     uint8_t *dstu8;
00266     int16_t *dst_int16_t;
00267     int32_t *dst_int32_t;
00268     int64_t *dst_int64_t;
00269     uint16_t *dst_uint16_t;
00270     uint32_t *dst_uint32_t;
00271 
00272     samples = data;
00273     src = buf;
00274 
00275     if (avctx->sample_fmt!=avctx->codec->sample_fmts[0]) {
00276         av_log(avctx, AV_LOG_ERROR, "invalid sample_fmt\n");
00277         return -1;
00278     }
00279 
00280     if(avctx->channels <= 0 || avctx->channels > MAX_CHANNELS){
00281         av_log(avctx, AV_LOG_ERROR, "PCM channels out of bounds\n");
00282         return -1;
00283     }
00284 
00285     sample_size = av_get_bits_per_sample(avctx->codec_id)/8;
00286 
00287     /* av_get_bits_per_sample returns 0 for CODEC_ID_PCM_DVD */
00288     if (CODEC_ID_PCM_DVD == avctx->codec_id)
00289         /* 2 samples are interleaved per block in PCM_DVD */
00290         sample_size = avctx->bits_per_coded_sample * 2 / 8;
00291     else if (avctx->codec_id == CODEC_ID_PCM_LXF)
00292         /* we process 40-bit blocks per channel for LXF */
00293         sample_size = 5;
00294 
00295     if (sample_size == 0) {
00296         av_log(avctx, AV_LOG_ERROR, "Invalid sample_size\n");
00297         return AVERROR(EINVAL);
00298     }
00299 
00300     n = avctx->channels * sample_size;
00301 
00302     if(n && buf_size % n){
00303         if (buf_size < n) {
00304             av_log(avctx, AV_LOG_ERROR, "invalid PCM packet\n");
00305             return -1;
00306         }else
00307             buf_size -= buf_size % n;
00308     }
00309 
00310     buf_size= FFMIN(buf_size, *data_size/2);
00311     *data_size=0;
00312 
00313     n = buf_size/sample_size;
00314 
00315     switch(avctx->codec->id) {
00316     case CODEC_ID_PCM_U32LE:
00317         DECODE(uint32_t, le32, src, samples, n, 0, 0x80000000)
00318         break;
00319     case CODEC_ID_PCM_U32BE:
00320         DECODE(uint32_t, be32, src, samples, n, 0, 0x80000000)
00321         break;
00322     case CODEC_ID_PCM_S24LE:
00323         DECODE(int32_t, le24, src, samples, n, 8, 0)
00324         break;
00325     case CODEC_ID_PCM_S24BE:
00326         DECODE(int32_t, be24, src, samples, n, 8, 0)
00327         break;
00328     case CODEC_ID_PCM_U24LE:
00329         DECODE(uint32_t, le24, src, samples, n, 8, 0x800000)
00330         break;
00331     case CODEC_ID_PCM_U24BE:
00332         DECODE(uint32_t, be24, src, samples, n, 8, 0x800000)
00333         break;
00334     case CODEC_ID_PCM_S24DAUD:
00335         for(;n>0;n--) {
00336           uint32_t v = bytestream_get_be24(&src);
00337           v >>= 4; // sync flags are here
00338           *samples++ = av_reverse[(v >> 8) & 0xff] +
00339                        (av_reverse[v & 0xff] << 8);
00340         }
00341         break;
00342     case CODEC_ID_PCM_S16LE_PLANAR:
00343         n /= avctx->channels;
00344         for(c=0;c<avctx->channels;c++)
00345             src2[c] = &src[c*n*2];
00346         for(;n>0;n--)
00347             for(c=0;c<avctx->channels;c++)
00348                 *samples++ = bytestream_get_le16(&src2[c]);
00349         src = src2[avctx->channels-1];
00350         break;
00351     case CODEC_ID_PCM_U16LE:
00352         DECODE(uint16_t, le16, src, samples, n, 0, 0x8000)
00353         break;
00354     case CODEC_ID_PCM_U16BE:
00355         DECODE(uint16_t, be16, src, samples, n, 0, 0x8000)
00356         break;
00357     case CODEC_ID_PCM_S8:
00358         dstu8= (uint8_t*)samples;
00359         for(;n>0;n--) {
00360             *dstu8++ = *src++ + 128;
00361         }
00362         samples= (short*)dstu8;
00363         break;
00364 #if HAVE_BIGENDIAN
00365     case CODEC_ID_PCM_F64LE:
00366         DECODE(int64_t, le64, src, samples, n, 0, 0)
00367         break;
00368     case CODEC_ID_PCM_S32LE:
00369     case CODEC_ID_PCM_F32LE:
00370         DECODE(int32_t, le32, src, samples, n, 0, 0)
00371         break;
00372     case CODEC_ID_PCM_S16LE:
00373         DECODE(int16_t, le16, src, samples, n, 0, 0)
00374         break;
00375     case CODEC_ID_PCM_F64BE:
00376     case CODEC_ID_PCM_F32BE:
00377     case CODEC_ID_PCM_S32BE:
00378     case CODEC_ID_PCM_S16BE:
00379 #else
00380     case CODEC_ID_PCM_F64BE:
00381         DECODE(int64_t, be64, src, samples, n, 0, 0)
00382         break;
00383     case CODEC_ID_PCM_F32BE:
00384     case CODEC_ID_PCM_S32BE:
00385         DECODE(int32_t, be32, src, samples, n, 0, 0)
00386         break;
00387     case CODEC_ID_PCM_S16BE:
00388         DECODE(int16_t, be16, src, samples, n, 0, 0)
00389         break;
00390     case CODEC_ID_PCM_F64LE:
00391     case CODEC_ID_PCM_F32LE:
00392     case CODEC_ID_PCM_S32LE:
00393     case CODEC_ID_PCM_S16LE:
00394 #endif /* HAVE_BIGENDIAN */
00395     case CODEC_ID_PCM_U8:
00396         memcpy(samples, src, n*sample_size);
00397         src += n*sample_size;
00398         samples = (short*)((uint8_t*)data + n*sample_size);
00399         break;
00400     case CODEC_ID_PCM_ZORK:
00401         for(;n>0;n--) {
00402             int x= *src++;
00403             if(x&128) x-= 128;
00404             else      x = -x;
00405             *samples++ = x << 8;
00406         }
00407         break;
00408     case CODEC_ID_PCM_ALAW:
00409     case CODEC_ID_PCM_MULAW:
00410         for(;n>0;n--) {
00411             *samples++ = s->table[*src++];
00412         }
00413         break;
00414     case CODEC_ID_PCM_DVD:
00415         dst_int32_t = data;
00416         n /= avctx->channels;
00417         switch (avctx->bits_per_coded_sample) {
00418         case 20:
00419             while (n--) {
00420                 c = avctx->channels;
00421                 src8 = src + 4*c;
00422                 while (c--) {
00423                     *dst_int32_t++ = (bytestream_get_be16(&src) << 16) + ((*src8   &0xf0) << 8);
00424                     *dst_int32_t++ = (bytestream_get_be16(&src) << 16) + ((*src8++ &0x0f) << 12);
00425                 }
00426                 src = src8;
00427             }
00428             break;
00429         case 24:
00430             while (n--) {
00431                 c = avctx->channels;
00432                 src8 = src + 4*c;
00433                 while (c--) {
00434                     *dst_int32_t++ = (bytestream_get_be16(&src) << 16) + ((*src8++) << 8);
00435                     *dst_int32_t++ = (bytestream_get_be16(&src) << 16) + ((*src8++) << 8);
00436                 }
00437                 src = src8;
00438             }
00439             break;
00440         default:
00441             av_log(avctx, AV_LOG_ERROR, "PCM DVD unsupported sample depth\n");
00442             return -1;
00443             break;
00444         }
00445         samples = (short *) dst_int32_t;
00446         break;
00447     case CODEC_ID_PCM_LXF:
00448         dst_int32_t = data;
00449         n /= avctx->channels;
00450         //unpack and de-planerize
00451         for (i = 0; i < n; i++) {
00452             for (c = 0, src8 = src + i*5; c < avctx->channels; c++, src8 += n*5) {
00453                 //extract low 20 bits and expand to 32 bits
00454                 *dst_int32_t++ = (src8[2] << 28) | (src8[1] << 20) | (src8[0] << 12) |
00455                                  ((src8[2] & 0xF) << 8) | src8[1];
00456             }
00457 
00458             for (c = 0, src8 = src + i*5; c < avctx->channels; c++, src8 += n*5) {
00459                 //extract high 20 bits and expand to 32 bits
00460                 *dst_int32_t++ = (src8[4] << 24) | (src8[3] << 16) |
00461                                  ((src8[2] & 0xF0) << 8) | (src8[4] << 4) | (src8[3] >> 4);
00462             }
00463         }
00464         src += n * avctx->channels * 5;
00465         samples = (short *) dst_int32_t;
00466         break;
00467     default:
00468         return -1;
00469     }
00470     *data_size = (uint8_t *)samples - (uint8_t *)data;
00471     return src - buf;
00472 }
00473 
00474 #if CONFIG_ENCODERS
00475 #define PCM_ENCODER(id_,sample_fmt_,name_,long_name_) \
00476 AVCodec ff_ ## name_ ## _encoder = {            \
00477     .name        = #name_,                      \
00478     .type        = AVMEDIA_TYPE_AUDIO,          \
00479     .id          = id_,                         \
00480     .init        = pcm_encode_init,             \
00481     .encode      = pcm_encode_frame,            \
00482     .close       = pcm_encode_close,            \
00483     .sample_fmts = (const enum AVSampleFormat[]){sample_fmt_,AV_SAMPLE_FMT_NONE}, \
00484     .long_name = NULL_IF_CONFIG_SMALL(long_name_), \
00485 }
00486 #else
00487 #define PCM_ENCODER(id,sample_fmt_,name,long_name_)
00488 #endif
00489 
00490 #if CONFIG_DECODERS
00491 #define PCM_DECODER(id_,sample_fmt_,name_,long_name_)         \
00492 AVCodec ff_ ## name_ ## _decoder = {            \
00493     .name           = #name_,                   \
00494     .type           = AVMEDIA_TYPE_AUDIO,       \
00495     .id             = id_,                      \
00496     .priv_data_size = sizeof(PCMDecode),        \
00497     .init           = pcm_decode_init,          \
00498     .decode         = pcm_decode_frame,         \
00499     .sample_fmts = (const enum AVSampleFormat[]){sample_fmt_,AV_SAMPLE_FMT_NONE}, \
00500     .long_name = NULL_IF_CONFIG_SMALL(long_name_), \
00501 }
00502 #else
00503 #define PCM_DECODER(id,sample_fmt_,name,long_name_)
00504 #endif
00505 
00506 #define PCM_CODEC(id, sample_fmt_, name, long_name_)         \
00507     PCM_ENCODER(id,sample_fmt_,name,long_name_); PCM_DECODER(id,sample_fmt_,name,long_name_)
00508 
00509 /* Note: Do not forget to add new entries to the Makefile as well. */
00510 PCM_CODEC  (CODEC_ID_PCM_ALAW,  AV_SAMPLE_FMT_S16, pcm_alaw, "PCM A-law");
00511 PCM_DECODER(CODEC_ID_PCM_DVD,   AV_SAMPLE_FMT_S32, pcm_dvd, "PCM signed 20|24-bit big-endian");
00512 PCM_CODEC  (CODEC_ID_PCM_F32BE, AV_SAMPLE_FMT_FLT, pcm_f32be, "PCM 32-bit floating point big-endian");
00513 PCM_CODEC  (CODEC_ID_PCM_F32LE, AV_SAMPLE_FMT_FLT, pcm_f32le, "PCM 32-bit floating point little-endian");
00514 PCM_CODEC  (CODEC_ID_PCM_F64BE, AV_SAMPLE_FMT_DBL, pcm_f64be, "PCM 64-bit floating point big-endian");
00515 PCM_CODEC  (CODEC_ID_PCM_F64LE, AV_SAMPLE_FMT_DBL, pcm_f64le, "PCM 64-bit floating point little-endian");
00516 PCM_DECODER(CODEC_ID_PCM_LXF,   AV_SAMPLE_FMT_S32, pcm_lxf, "PCM signed 20-bit little-endian planar");
00517 PCM_CODEC  (CODEC_ID_PCM_MULAW, AV_SAMPLE_FMT_S16, pcm_mulaw, "PCM mu-law");
00518 PCM_CODEC  (CODEC_ID_PCM_S8,    AV_SAMPLE_FMT_U8,  pcm_s8, "PCM signed 8-bit");
00519 PCM_CODEC  (CODEC_ID_PCM_S16BE, AV_SAMPLE_FMT_S16, pcm_s16be, "PCM signed 16-bit big-endian");
00520 PCM_CODEC  (CODEC_ID_PCM_S16LE, AV_SAMPLE_FMT_S16, pcm_s16le, "PCM signed 16-bit little-endian");
00521 PCM_DECODER(CODEC_ID_PCM_S16LE_PLANAR, AV_SAMPLE_FMT_S16, pcm_s16le_planar, "PCM 16-bit little-endian planar");
00522 PCM_CODEC  (CODEC_ID_PCM_S24BE, AV_SAMPLE_FMT_S32, pcm_s24be, "PCM signed 24-bit big-endian");
00523 PCM_CODEC  (CODEC_ID_PCM_S24DAUD, AV_SAMPLE_FMT_S16,  pcm_s24daud, "PCM D-Cinema audio signed 24-bit");
00524 PCM_CODEC  (CODEC_ID_PCM_S24LE, AV_SAMPLE_FMT_S32, pcm_s24le, "PCM signed 24-bit little-endian");
00525 PCM_CODEC  (CODEC_ID_PCM_S32BE, AV_SAMPLE_FMT_S32, pcm_s32be, "PCM signed 32-bit big-endian");
00526 PCM_CODEC  (CODEC_ID_PCM_S32LE, AV_SAMPLE_FMT_S32, pcm_s32le, "PCM signed 32-bit little-endian");
00527 PCM_CODEC  (CODEC_ID_PCM_U8,    AV_SAMPLE_FMT_U8,  pcm_u8, "PCM unsigned 8-bit");
00528 PCM_CODEC  (CODEC_ID_PCM_U16BE, AV_SAMPLE_FMT_S16, pcm_u16be, "PCM unsigned 16-bit big-endian");
00529 PCM_CODEC  (CODEC_ID_PCM_U16LE, AV_SAMPLE_FMT_S16, pcm_u16le, "PCM unsigned 16-bit little-endian");
00530 PCM_CODEC  (CODEC_ID_PCM_U24BE, AV_SAMPLE_FMT_S32, pcm_u24be, "PCM unsigned 24-bit big-endian");
00531 PCM_CODEC  (CODEC_ID_PCM_U24LE, AV_SAMPLE_FMT_S32, pcm_u24le, "PCM unsigned 24-bit little-endian");
00532 PCM_CODEC  (CODEC_ID_PCM_U32BE, AV_SAMPLE_FMT_S32, pcm_u32be, "PCM unsigned 32-bit big-endian");
00533 PCM_CODEC  (CODEC_ID_PCM_U32LE, AV_SAMPLE_FMT_S32, pcm_u32le, "PCM unsigned 32-bit little-endian");
00534 PCM_CODEC  (CODEC_ID_PCM_ZORK,  AV_SAMPLE_FMT_S16, pcm_zork, "PCM Zork");