Libav 0.7.1
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00001 /* 00002 * RoQ audio encoder 00003 * 00004 * Copyright (c) 2005 Eric Lasota 00005 * Based on RoQ specs (c)2001 Tim Ferguson 00006 * 00007 * This file is part of Libav. 00008 * 00009 * Libav is free software; you can redistribute it and/or 00010 * modify it under the terms of the GNU Lesser General Public 00011 * License as published by the Free Software Foundation; either 00012 * version 2.1 of the License, or (at your option) any later version. 00013 * 00014 * Libav is distributed in the hope that it will be useful, 00015 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00016 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00017 * Lesser General Public License for more details. 00018 * 00019 * You should have received a copy of the GNU Lesser General Public 00020 * License along with Libav; if not, write to the Free Software 00021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00022 */ 00023 00024 #include "libavutil/intmath.h" 00025 #include "avcodec.h" 00026 #include "bytestream.h" 00027 00028 #define ROQ_FIRST_FRAME_SIZE (735*8) 00029 #define ROQ_FRAME_SIZE 735 00030 00031 00032 #define MAX_DPCM (127*127) 00033 00034 00035 typedef struct 00036 { 00037 short lastSample[2]; 00038 } ROQDPCMContext; 00039 00040 static av_cold int roq_dpcm_encode_init(AVCodecContext *avctx) 00041 { 00042 ROQDPCMContext *context = avctx->priv_data; 00043 00044 if (avctx->channels > 2) { 00045 av_log(avctx, AV_LOG_ERROR, "Audio must be mono or stereo\n"); 00046 return -1; 00047 } 00048 if (avctx->sample_rate != 22050) { 00049 av_log(avctx, AV_LOG_ERROR, "Audio must be 22050 Hz\n"); 00050 return -1; 00051 } 00052 if (avctx->sample_fmt != AV_SAMPLE_FMT_S16) { 00053 av_log(avctx, AV_LOG_ERROR, "Audio must be signed 16-bit\n"); 00054 return -1; 00055 } 00056 00057 avctx->frame_size = ROQ_FIRST_FRAME_SIZE; 00058 00059 context->lastSample[0] = context->lastSample[1] = 0; 00060 00061 avctx->coded_frame= avcodec_alloc_frame(); 00062 avctx->coded_frame->key_frame= 1; 00063 00064 return 0; 00065 } 00066 00067 static unsigned char dpcm_predict(short *previous, short current) 00068 { 00069 int diff; 00070 int negative; 00071 int result; 00072 int predicted; 00073 00074 diff = current - *previous; 00075 00076 negative = diff<0; 00077 diff = FFABS(diff); 00078 00079 if (diff >= MAX_DPCM) 00080 result = 127; 00081 else { 00082 result = ff_sqrt(diff); 00083 result += diff > result*result+result; 00084 } 00085 00086 /* See if this overflows */ 00087 retry: 00088 diff = result*result; 00089 if (negative) 00090 diff = -diff; 00091 predicted = *previous + diff; 00092 00093 /* If it overflows, back off a step */ 00094 if (predicted > 32767 || predicted < -32768) { 00095 result--; 00096 goto retry; 00097 } 00098 00099 /* Add the sign bit */ 00100 result |= negative << 7; //if (negative) result |= 128; 00101 00102 *previous = predicted; 00103 00104 return result; 00105 } 00106 00107 static int roq_dpcm_encode_frame(AVCodecContext *avctx, 00108 unsigned char *frame, int buf_size, void *data) 00109 { 00110 int i, samples, stereo, ch; 00111 const short *in; 00112 unsigned char *out; 00113 00114 ROQDPCMContext *context = avctx->priv_data; 00115 00116 stereo = (avctx->channels == 2); 00117 00118 if (stereo) { 00119 context->lastSample[0] &= 0xFF00; 00120 context->lastSample[1] &= 0xFF00; 00121 } 00122 00123 out = frame; 00124 in = data; 00125 00126 bytestream_put_byte(&out, stereo ? 0x21 : 0x20); 00127 bytestream_put_byte(&out, 0x10); 00128 bytestream_put_le32(&out, avctx->frame_size*avctx->channels); 00129 00130 if (stereo) { 00131 bytestream_put_byte(&out, (context->lastSample[1])>>8); 00132 bytestream_put_byte(&out, (context->lastSample[0])>>8); 00133 } else 00134 bytestream_put_le16(&out, context->lastSample[0]); 00135 00136 /* Write the actual samples */ 00137 samples = avctx->frame_size; 00138 for (i=0; i<samples; i++) 00139 for (ch=0; ch<avctx->channels; ch++) 00140 *out++ = dpcm_predict(&context->lastSample[ch], *in++); 00141 00142 /* Use smaller frames from now on */ 00143 avctx->frame_size = ROQ_FRAME_SIZE; 00144 00145 /* Return the result size */ 00146 return out - frame; 00147 } 00148 00149 static av_cold int roq_dpcm_encode_close(AVCodecContext *avctx) 00150 { 00151 av_freep(&avctx->coded_frame); 00152 00153 return 0; 00154 } 00155 00156 AVCodec ff_roq_dpcm_encoder = { 00157 "roq_dpcm", 00158 AVMEDIA_TYPE_AUDIO, 00159 CODEC_ID_ROQ_DPCM, 00160 sizeof(ROQDPCMContext), 00161 roq_dpcm_encode_init, 00162 roq_dpcm_encode_frame, 00163 roq_dpcm_encode_close, 00164 NULL, 00165 .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, 00166 .long_name = NULL_IF_CONFIG_SMALL("id RoQ DPCM"), 00167 };