static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, AVPacket *avpkt) { const uint8_t *buf = avpkt->data; int buf_size = avpkt->size; AC3DecodeContext *s = avctx->priv_data; int16_t *out_samples = (int16_t *)data; int blk, ch, err; const uint8_t *channel_map; const float *output[AC3_MAX_CHANNELS]; /* initialize the GetBitContext with the start of valid AC-3 Frame */ if (s->input_buffer) { /* copy input buffer to decoder context to avoid reading past the end of the buffer, which can be caused by a damaged input stream. */ memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_FRAME_BUFFER_SIZE)); init_get_bits(&s->gbc, s->input_buffer, buf_size * 8); } else { init_get_bits(&s->gbc, buf, buf_size * 8); } /* parse the syncinfo */ *data_size = 0; err = parse_frame_header(s); if (err) { switch(err) { case AAC_AC3_PARSE_ERROR_SYNC: av_log(avctx, AV_LOG_ERROR, "frame sync error\n"); return -1; case AAC_AC3_PARSE_ERROR_BSID: av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n"); break; case AAC_AC3_PARSE_ERROR_SAMPLE_RATE: av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n"); break; case AAC_AC3_PARSE_ERROR_FRAME_SIZE: av_log(avctx, AV_LOG_ERROR, "invalid frame size\n"); break; case AAC_AC3_PARSE_ERROR_FRAME_TYPE: /* skip frame if CRC is ok. otherwise use error concealment. */ /* TODO: add support for substreams and dependent frames */ if(s->frame_type == EAC3_FRAME_TYPE_DEPENDENT || s->substreamid) { av_log(avctx, AV_LOG_ERROR, "unsupported frame type : skipping frame\n"); return s->frame_size; } else { av_log(avctx, AV_LOG_ERROR, "invalid frame type\n"); } break; default: av_log(avctx, AV_LOG_ERROR, "invalid header\n"); break; } } else { /* check that reported frame size fits in input buffer */ if (s->frame_size > buf_size) { av_log(avctx, AV_LOG_ERROR, "incomplete frame\n"); err = AAC_AC3_PARSE_ERROR_FRAME_SIZE; } else if (avctx->error_recognition >= FF_ER_CAREFUL) { /* check for crc mismatch */ if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) { av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n"); err = AAC_AC3_PARSE_ERROR_CRC; } } } /* if frame is ok, set audio parameters */ if (!err) { avctx->sample_rate = s->sample_rate; avctx->bit_rate = s->bit_rate; /* channel config */ s->out_channels = s->channels; s->output_mode = s->channel_mode; if(s->lfe_on) s->output_mode |= AC3_OUTPUT_LFEON; if (avctx->request_channels > 0 && avctx->request_channels <= 2 && avctx->request_channels < s->channels) { s->out_channels = avctx->request_channels; s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO; s->channel_layout = ff_ac3_channel_layout_tab[s->output_mode]; } avctx->channels = s->out_channels; avctx->channel_layout = s->channel_layout; /* set downmixing coefficients if needed */ if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) && s->fbw_channels == s->out_channels)) { set_downmix_coeffs(s); } } else if (!s->out_channels) { s->out_channels = avctx->channels; if(s->out_channels < s->channels) s->output_mode = s->out_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO; } /* decode the audio blocks */ channel_map = ff_ac3_dec_channel_map[s->output_mode & ~AC3_OUTPUT_LFEON][s->lfe_on]; for (ch = 0; ch < s->out_channels; ch++) output[ch] = s->output[channel_map[ch]]; for (blk = 0; blk < s->num_blocks; blk++) { if (!err && decode_audio_block(s, blk)) { av_log(avctx, AV_LOG_ERROR, "error decoding the audio block\n"); err = 1; } s->fmt_conv.float_to_int16_interleave(out_samples, output, 256, s->out_channels); out_samples += 256 * s->out_channels; } *data_size = s->num_blocks * 256 * avctx->channels * sizeof (int16_t); return FFMIN(buf_size, s->frame_size); }