libavcodec/s302m.c
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00001 /*
00002  * SMPTE 302M decoder
00003  * Copyright (c) 2008 Laurent Aimar <fenrir@videolan.org>
00004  * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
00005  *
00006  * This file is part of Libav.
00007  *
00008  * Libav is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * Libav is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with Libav; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "libavutil/intreadwrite.h"
00024 #include "avcodec.h"
00025 #include "internal.h"
00026 
00027 #define AES3_HEADER_LEN 4
00028 
00029 typedef struct S302MDecodeContext {
00030     AVFrame frame;
00031 } S302MDecodeContext;
00032 
00033 static int s302m_parse_frame_header(AVCodecContext *avctx, const uint8_t *buf,
00034                                     int buf_size)
00035 {
00036     uint32_t h;
00037     int frame_size, channels, bits;
00038 
00039     if (buf_size <= AES3_HEADER_LEN) {
00040         av_log(avctx, AV_LOG_ERROR, "frame is too short\n");
00041         return AVERROR_INVALIDDATA;
00042     }
00043 
00044     /*
00045      * AES3 header :
00046      * size:            16
00047      * number channels   2
00048      * channel_id        8
00049      * bits per samples  2
00050      * alignments        4
00051      */
00052 
00053     h = AV_RB32(buf);
00054     frame_size =  (h >> 16) & 0xffff;
00055     channels   = ((h >> 14) & 0x0003) * 2 +  2;
00056     bits       = ((h >>  4) & 0x0003) * 4 + 16;
00057 
00058     if (AES3_HEADER_LEN + frame_size != buf_size || bits > 24) {
00059         av_log(avctx, AV_LOG_ERROR, "frame has invalid header\n");
00060         return AVERROR_INVALIDDATA;
00061     }
00062 
00063     /* Set output properties */
00064     avctx->bits_per_coded_sample = bits;
00065     if (bits > 16)
00066         avctx->sample_fmt = AV_SAMPLE_FMT_S32;
00067     else
00068         avctx->sample_fmt = AV_SAMPLE_FMT_S16;
00069 
00070     avctx->channels    = channels;
00071     avctx->sample_rate = 48000;
00072     avctx->bit_rate    = 48000 * avctx->channels * (avctx->bits_per_coded_sample + 4) +
00073                          32 * (48000 / (buf_size * 8 /
00074                                         (avctx->channels *
00075                                          (avctx->bits_per_coded_sample + 4))));
00076 
00077     return frame_size;
00078 }
00079 
00080 static int s302m_decode_frame(AVCodecContext *avctx, void *data,
00081                               int *got_frame_ptr, AVPacket *avpkt)
00082 {
00083     S302MDecodeContext *s = avctx->priv_data;
00084     const uint8_t *buf = avpkt->data;
00085     int buf_size       = avpkt->size;
00086     int block_size, ret;
00087 
00088     int frame_size = s302m_parse_frame_header(avctx, buf, buf_size);
00089     if (frame_size < 0)
00090         return frame_size;
00091 
00092     buf_size -= AES3_HEADER_LEN;
00093     buf      += AES3_HEADER_LEN;
00094 
00095     /* get output buffer */
00096     block_size = (avctx->bits_per_coded_sample + 4) / 4;
00097     s->frame.nb_samples = 2 * (buf_size / block_size) / avctx->channels;
00098     if ((ret = ff_get_buffer(avctx, &s->frame)) < 0) {
00099         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
00100         return ret;
00101     }
00102 
00103     buf_size = (s->frame.nb_samples * avctx->channels / 2) * block_size;
00104 
00105     if (avctx->bits_per_coded_sample == 24) {
00106         uint32_t *o = (uint32_t *)s->frame.data[0];
00107         for (; buf_size > 6; buf_size -= 7) {
00108             *o++ = (av_reverse[buf[2]]        << 24) |
00109                    (av_reverse[buf[1]]        << 16) |
00110                    (av_reverse[buf[0]]        <<  8);
00111             *o++ = (av_reverse[buf[6] & 0xf0] << 28) |
00112                    (av_reverse[buf[5]]        << 20) |
00113                    (av_reverse[buf[4]]        << 12) |
00114                    (av_reverse[buf[3] & 0x0f] <<  4);
00115             buf += 7;
00116         }
00117     } else if (avctx->bits_per_coded_sample == 20) {
00118         uint32_t *o = (uint32_t *)s->frame.data[0];
00119         for (; buf_size > 5; buf_size -= 6) {
00120             *o++ = (av_reverse[buf[2] & 0xf0] << 28) |
00121                    (av_reverse[buf[1]]        << 20) |
00122                    (av_reverse[buf[0]]        << 12);
00123             *o++ = (av_reverse[buf[5] & 0xf0] << 28) |
00124                    (av_reverse[buf[4]]        << 20) |
00125                    (av_reverse[buf[3]]        << 12);
00126             buf += 6;
00127         }
00128     } else {
00129         uint16_t *o = (uint16_t *)s->frame.data[0];
00130         for (; buf_size > 4; buf_size -= 5) {
00131             *o++ = (av_reverse[buf[1]]        <<  8) |
00132                     av_reverse[buf[0]];
00133             *o++ = (av_reverse[buf[4] & 0xf0] << 12) |
00134                    (av_reverse[buf[3]]        <<  4) |
00135                    (av_reverse[buf[2]]        >>  4);
00136             buf += 5;
00137         }
00138     }
00139 
00140     *got_frame_ptr   = 1;
00141     *(AVFrame *)data = s->frame;
00142 
00143     return avpkt->size;
00144 }
00145 
00146 static int s302m_decode_init(AVCodecContext *avctx)
00147 {
00148     S302MDecodeContext *s = avctx->priv_data;
00149 
00150     avcodec_get_frame_defaults(&s->frame);
00151     avctx->coded_frame = &s->frame;
00152 
00153     return 0;
00154 }
00155 
00156 
00157 AVCodec ff_s302m_decoder = {
00158     .name           = "s302m",
00159     .type           = AVMEDIA_TYPE_AUDIO,
00160     .id             = CODEC_ID_S302M,
00161     .priv_data_size = sizeof(S302MDecodeContext),
00162     .init           = s302m_decode_init,
00163     .decode         = s302m_decode_frame,
00164     .capabilities   = CODEC_CAP_DR1,
00165     .long_name      = NULL_IF_CONFIG_SMALL("SMPTE 302M"),
00166 };