1/* 2 * PCM common functions 3 * Copyright (c) 2003 Fabrice Bellard 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * FFmpeg is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22#include "libavutil/mathematics.h" 23#include "avformat.h" 24#include "internal.h" 25#include "pcm.h" 26 27#define RAW_SAMPLES 1024 28 29int ff_pcm_read_packet(AVFormatContext *s, AVPacket *pkt) 30{ 31 AVCodecParameters *par = s->streams[0]->codecpar; 32 int ret, size; 33 34 if (par->block_align <= 0) 35 return AVERROR(EINVAL); 36 37 /* 38 * Compute read size to complete a read every 62ms. 39 * Clamp to RAW_SAMPLES if larger. 40 */ 41 size = FFMAX(par->sample_rate/25, 1); 42 if (par->block_align <= INT_MAX / RAW_SAMPLES) { 43 size = FFMIN(size, RAW_SAMPLES) * par->block_align; 44 } else { 45 size = par->block_align; 46 } 47 48 ret = av_get_packet(s->pb, pkt, size); 49 50 pkt->flags &= ~AV_PKT_FLAG_CORRUPT; 51 pkt->stream_index = 0; 52 53 return ret; 54} 55 56int ff_pcm_read_seek(AVFormatContext *s, 57 int stream_index, int64_t timestamp, int flags) 58{ 59 AVStream *st; 60 int block_align, byte_rate; 61 int64_t pos, ret; 62 63 st = s->streams[0]; 64 65 block_align = st->codecpar->block_align ? st->codecpar->block_align : 66 (av_get_bits_per_sample(st->codecpar->codec_id) * st->codecpar->ch_layout.nb_channels) >> 3; 67 byte_rate = st->codecpar->bit_rate ? st->codecpar->bit_rate >> 3 : 68 block_align * st->codecpar->sample_rate; 69 70 if (block_align <= 0 || byte_rate <= 0) 71 return -1; 72 if (timestamp < 0) timestamp = 0; 73 74 /* compute the position by aligning it to block_align */ 75 pos = av_rescale_rnd(timestamp * byte_rate, 76 st->time_base.num, 77 st->time_base.den * (int64_t)block_align, 78 (flags & AVSEEK_FLAG_BACKWARD) ? AV_ROUND_DOWN : AV_ROUND_UP); 79 pos *= block_align; 80 81 /* recompute exact position */ 82 ffstream(st)->cur_dts = av_rescale(pos, st->time_base.den, byte_rate * (int64_t)st->time_base.num); 83 if ((ret = avio_seek(s->pb, pos + ffformatcontext(s)->data_offset, SEEK_SET)) < 0) 84 return ret; 85 return 0; 86} 87