zoukankan      html  css  js  c++  java
  • opus 规范 与参数解析

    bytestream_put_buffer(&p, "OpusHead", 8);
    bytestream_put_byte(&p, 1); /* Version */
    bytestream_put_byte(&p, channels);
    bytestream_put_le16(&p, avctx->initial_padding); /* Lookahead samples at 48kHz */
    bytestream_put_le32(&p, avctx->sample_rate); /* Original sample rate */
    Data Fields
    1 int OpusHead::version 1个字节
    The Ogg Opus format version, in the range 0...255.
    The top 4 bits represent a "major" version, and the bottom four bits represent
    backwards-compatible "minor" revisions. The current specification describes version
    1. This library will recognize versions up through 15 as backwards compatible with
    the current specification. An earlier draft of the specification described a version 0, but
    the only difference between version 1 and version 0 is that version 0 did not specify the
    semantics for handling the version field.

    2 int OpusHead::channel_count
    The number of channels, in the range 1...255.
    3 unsigned OpusHead::pre_skip =2字节
    The number of samples that should be discarded丢弃 from the beginning of the stream.
    4 opus uint32 OpusHead::input_sample_rate
    The sampling rate of the original input.
    All Opus audio is coded at 48 kHz, and should also be decoded at 48 kHz for playback
    (unless the target hardware does not support this sampling rate). However, this field
    may be used to resample the audio back to the original sampling rate, for example,
    when saving the output to a file.
    5 int OpusHead::output_gain
    The gain to apply to the decoded output, in dB, as a Q8 value in the range.
    -32768...32767. The decoder will automatically scale the output by pow(10,output_-
    gain/(20.0256)).
    6 int OpusHead::mapping_family
    The channel mapping family, in the range 0...255.
    Channel mapping family 0 covers mono or stereo in a single stream. Channel mapping
    family 1 covers 1 to 8 channels in one or more streams, using the Vorbis speaker
    assignments. Channel mapping family 255 covers 1 to 255 channels in one or more
    streams, but without any defined speaker assignment.
    7 int OpusHead::stream_count
    The number of Opus streams in each Ogg packet, in the range 1...255.
    8 int OpusHead::coupled_count
    The number of coupled Opus streams in each Ogg packet, in the range 0...127.
    This must satisfy 0 <= coupled_count <= stream_count and coupled-
    _count + stream_count <= 255. The coupled streams appear first, before
    all uncoupled streams, in an Ogg Opus packet.
    9 unsigned char OpusHead::mapping[OPUS_CHANNEL_COUNT_MAX]
    The mapping from coded stream channels to output channels.
    Let index=mapping[k] be the value for channel k. If index<2coupled_-
    count, then it refers to the left channel from stream (index/2) if even, and the
    right channel from stream (index/2) if odd. Otherwise, it refers to the output of the
    uncoupled stream (index-coupled_count).
    opus_head_parse
    ffmpeg的extradata
    #define OPUS_HEAD_SIZE 19
    Total:      19 ( 0x00000013 )
    4F, 70, 75, 73, 48, 65, 61, 64,  01=version, 01=channels, (68, 00), 80, 3E, 00, 00, 
    (00, 00), 00,    //OpusHead..h..>.....
    bytestream_put_le16
    解析通道数和采样率
    int ch = audioCtx->extradata[9];
     uint32_t hz=*(uint32_t*)&(audioCtx->extradata[12]);
    aac 参数包大小4+11+2+2=19
    opus=4+11+2+19=36
    解析:
    avc->channels = avc->extradata_size >= 10 ? avc->extradata[9] : (avc->channels == 1) ? 1 : 2;
    参考:
    opusfile_api-0.2(opus 规范).pdf
  • 相关阅读:
    认识hammer.js
    Mac使用Charles进行HTTPS抓包
    CentOS7下安装Python3及Pip3并保留Python2
    CenOS7.4内核升级修复系统漏洞
    PHP连接不上MySQL解决方案总结
    linux安装redis
    图片上传的两种实现方式
    python笔记6 模块与包 程序开发规范 包 re sys time os模块
    python Image 模块处理图片
    python笔记5 接口类抽象类 封装 反射 设计模式 模块 :random随机数 josn shelve持久化存储
  • 原文地址:https://www.cnblogs.com/elesos/p/7799074.html
Copyright © 2011-2022 走看看