音视频领域中， 5.1 7.1声道不同版本的区别 ---- 5.1 5.1(side) 7.1 7.1(side) 7.1(wide-side)

先参见FFmpeg代码

    { "5.1",            AV_CHANNEL_LAYOUT_5POINT1_BACK        },
    { "5.1(side)",      AV_CHANNEL_LAYOUT_5POINT1             },

    { "7.1",            AV_CHANNEL_LAYOUT_7POINT1             },
    { "7.1(wide)",      AV_CHANNEL_LAYOUT_7POINT1_WIDE_BACK   },
    { "7.1(wide-side)", AV_CHANNEL_LAYOUT_7POINT1_WIDE        },

5.0声道相关代码

#define AV_CH_LAYOUT_5POINT0           (AV_CH_LAYOUT_SURROUND|AV_CH_SIDE_LEFT|AV_CH_SIDE_RIGHT)
#define AV_CH_LAYOUT_5POINT0_BACK      (AV_CH_LAYOUT_SURROUND|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT)

#define AV_CHANNEL_LAYOUT_5POINT0           AV_CHANNEL_LAYOUT_MASK(5,  AV_CH_LAYOUT_5POINT0)
#define AV_CHANNEL_LAYOUT_5POINT0_BACK      AV_CHANNEL_LAYOUT_MASK(5,  AV_CH_LAYOUT_5POINT0_BACK)

• 可以看到5.1声道有两个声道在后面，而5.1（side）两个声道在左右两边
• 5.1（side）是没有后面的声道的！！

7.0、7.1声道相关代码

#define AV_CH_LAYOUT_7POINT1           (AV_CH_LAYOUT_5POINT1|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT)
#define AV_CH_LAYOUT_7POINT1_WIDE      (AV_CH_LAYOUT_5POINT1|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER)
#define AV_CH_LAYOUT_7POINT1_WIDE_BACK (AV_CH_LAYOUT_5POINT1_BACK|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER)

• 可以看到7.1声道是5.1声道增加了左右两个声道得到的
  7.1 AV_CH_LAYOUT_5POINT1|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT
  7.1（wide） AV_CH_LAYOUT_5POINT1|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER
  7.1（wide-side）AV_CH_LAYOUT_5POINT1_BACK|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER
• 7.1（wide）没有后面的声道，其他都有