AVCodecParameters结构体

AVCodecParamteres结构体是将AVCodecContext中编解码器参数抽取出而形成的新的结构体，在新版本中的FFMPEG中，有些结构体中的AVCodecContext已经被弃用，取而代之的就是AVCodecParameters这个参数，该结构体定义在libavcodec/codec_par.h文件中，该结构体的定义如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
typedef struct AVCodecParameters {
 /**
 * General type of the encoded data.
 */
 enum AVMediaType codec_type;
 /**
 * Specific type of the encoded data (the codec used).
 */
 enum AVCodecID codec_id;
 /**
 * Additional information about the codec (corresponds to the AVI FOURCC).
 */
 uint32_t codec_tag;
 
 /**
 * Extra binary data needed for initializing the decoder, codec-dependent.
 *
 * Must be allocated with av_malloc() and will be freed by
 * avcodec_parameters_free(). The allocated size of extradata must be at
 * least extradata_size + AV_INPUT_BUFFER_PADDING_SIZE, with the padding
 * bytes zeroed.
 */
 uint8_t *extradata;
 /**
 * Size of the extradata content in bytes.
 */
 int extradata_size;
 
 /**
 * - video: the pixel format, the value corresponds to enum AVPixelFormat.
 * - audio: the sample format, the value corresponds to enum AVSampleFormat.
 */
 int format;
 
 /**
 * The average bitrate of the encoded data (in bits per second).
 */
 int64_t bit_rate;
 
 /**
 * The number of bits per sample in the codedwords.
 *
 * This is basically the bitrate per sample. It is mandatory for a bunch of
 * formats to actually decode them. It's the number of bits for one sample in
 * the actual coded bitstream.
 *
 * This could be for example 4 for ADPCM
 * For PCM formats this matches bits_per_raw_sample
 * Can be 0
 */
 int bits_per_coded_sample;
 
 /**
 * This is the number of valid bits in each output sample. If the
 * sample format has more bits, the least significant bits are additional
 * padding bits, which are always 0. Use right shifts to reduce the sample
 * to its actual size. For example, audio formats with 24 bit samples will
 * have bits_per_raw_sample set to 24, and format set to AV_SAMPLE_FMT_S32.
 * To get the original sample use "(int32_t)sample >> 8"."
 *
 * For ADPCM this might be 12 or 16 or similar
 * Can be 0
 */
 int bits_per_raw_sample;
 
 /**
 * Codec-specific bitstream restrictions that the stream conforms to.
  */
 int profile;
 int level;
 
 /**
 * Video only. The dimensions of the video frame in pixels.
 */
 int width;
 int height;
 
 /**
 * Video only. The aspect ratio (width / height) which a single pixel
 * should have when displayed.
 *
 * When the aspect ratio is unknown / undefined, the numerator should be
 * set to 0 (the denominator may have any value).
 */
 AVRational sample_aspect_ratio;
 
 /**
 * Video only. The order of the fields in interlaced video.
 */
 enum AVFieldOrder field_order;
 
 /**
 * Video only. Additional colorspace characteristics.
 */
 enum AVColorRange color_range;
 enum AVColorPrimaries color_primaries;
 enum AVColorTransferCharacteristic color_trc;
 enum AVColorSpace color_space;
 enum AVChromaLocation chroma_location;
 
 /**
 * Video only. Number of delayed frames.
 */
 int video_delay;
 
 /**
 * Audio only. The channel layout bitmask. May be 0 if the channel layout is
 * unknown or unspecified, otherwise the number of bits set must be equal to
 * the channels field.
 */
 uint64_t channel_layout;
 /**
 * Audio only. The number of audio channels.
 */
 int channels;
 /**
 * Audio only. The number of audio samples per second.
 */
 int sample_rate;
 /**
 * Audio only. The number of bytes per coded audio frame, required by some
 * formats.
  *
 * Corresponds to nBlockAlign in WAVEFORMATEX.
 */
 int block_align;
 /**
 * Audio only. Audio frame size, if known. Required by some formats to be static.
 */
 int frame_size;
 
 /**
 * Audio only. The amount of padding (in samples) inserted by the encoder at
 * the beginning of the audio. I.e. this number of leading decoded samples
 * must be discarded by the caller to get the original audio without leading
 * padding.
 */
 int initial_padding;
 /**
 * Audio only. The amount of padding (in samples) appended by the encoder to
 * the end of the audio. I.e. this number of decoded samples must be
 * discarded by the caller from the end of the stream to get the original
 * audio without any trailing padding.
 */
 int trailing_padding;
 /**
 * Audio only. Number of samples to skip after a discontinuity.
 */
 int seek_preroll;
} AVCodecParameters;

因为AVCodecContext结构体包含的参数太多，AVCodecParameters将编码器的参数从AVCodecContext分离出来，AVCodecParameters结构体中部分重要的参数如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
enum AVMediaType codec_type; 编解码器的类型 
const struct AVCodec *codec; 编解码器,初始化后不可更改
enum AVCodecID codec_id; 编解码器的id
int64_t bit_rate; 平均比特率
uint8_t *extradata; int extradata_size; 针对特定编码器包含的附加信息
AVRational time_base; 根据该参数可以将pts转化为实践
int width, height; 每一帧的宽和高
int gop_size; 一组图片的数量，编码时用户设置，解码时不使用
enum AVPixelFormat pix_fmt; 像素格式，编码时用户设置，解码时可由用户指定，但是在分析数据会被覆盖用户的设置
int refs; 参考帧的数量
enum AVColorSpace colorspace; YUV色彩空间类型
enum AVColorRange color_range; MPEG JPEG YUV范围
int sample_rate; 采样率 仅音频
int channels; 声道数（音频）
enum AVSampleFormat sample_fmt; //采样格式
int frame_size; 每个音频帧中每个声道的采样数量
int profile;配置类型
int level;级别
赏

谢谢你请我吃糖果

扫一扫，分享到微信

微信分享二维码

tag:

    缺失模块。
    1、请确保node版本大于6.2
    2、在博客根目录（注意不是yilia根目录）执行以下命令：
    npm i hexo-generator-json-content --save

    3、在根目录_config.yml里添加配置： 

      jsonContent:
    meta: false
    pages: false
    posts:
      title: true
      date: true
      path: true
      text: false
      raw: false
      content: false
      slug: false
      updated: false
      comments: false
      link: false
      permalink: false
      excerpt: false
      categories: false
      tags: true

I am what I am