通道布局与通用函数
目录
类型和枚举说明
channel_masks Audio channel masks通道掩码
#define AV_CH_FRONT_LEFT 0x00000001
#define AV_CH_FRONT_RIGHT 0x00000002
#define AV_CH_FRONT_CENTER 0x00000004
#define AV_CH_LOW_FREQUENCY 0x00000008
#define AV_CH_BACK_LEFT 0x00000010
#define AV_CH_BACK_RIGHT 0x00000020
#define AV_CH_FRONT_LEFT_OF_CENTER 0x00000040
#define AV_CH_FRONT_RIGHT_OF_CENTER 0x00000080
#define AV_CH_BACK_CENTER 0x00000100
#define AV_CH_SIDE_LEFT 0x00000200
#define AV_CH_SIDE_RIGHT 0x00000400
#define AV_CH_TOP_CENTER 0x00000800
#define AV_CH_TOP_FRONT_LEFT 0x00001000
#define AV_CH_TOP_FRONT_CENTER 0x00002000
#define AV_CH_TOP_FRONT_RIGHT 0x00004000
#define AV_CH_TOP_BACK_LEFT 0x00008000
#define AV_CH_TOP_BACK_CENTER 0x00010000
#define AV_CH_TOP_BACK_RIGHT 0x00020000
#define AV_CH_STEREO_LEFT 0x20000000 ///< Stereo downmix.
#define AV_CH_STEREO_RIGHT 0x40000000 ///< See AV_CH_STEREO_LEFT.
#define AV_CH_WIDE_LEFT 0x0000000080000000ULL
#define AV_CH_WIDE_RIGHT 0x0000000100000000ULL
#define AV_CH_SURROUND_DIRECT_LEFT 0x0000000200000000ULL
#define AV_CH_SURROUND_DIRECT_RIGHT 0x0000000400000000ULL
#define AV_CH_LOW_FREQUENCY_2 0x0000000800000000ULL
/** Channel mask value used for AVCodecContext.request_channel_layout
to indicate that the user requests the channel order of the decoder output
to be the native codec channel order. */
#define AV_CH_LAYOUT_NATIVE 0x8000000000000000ULL
channel_mask_c Audio channel layouts通道布局
#define AV_CH_LAYOUT_MONO (AV_CH_FRONT_CENTER)
#define AV_CH_LAYOUT_STEREO (AV_CH_FRONT_LEFT|AV_CH_FRONT_RIGHT)
#define AV_CH_LAYOUT_2POINT1 (AV_CH_LAYOUT_STEREO|AV_CH_LOW_FREQUENCY)
#define AV_CH_LAYOUT_2_1 (AV_CH_LAYOUT_STEREO|AV_CH_BACK_CENTER)
#define AV_CH_LAYOUT_SURROUND (AV_CH_LAYOUT_STEREO|AV_CH_FRONT_CENTER)
#define AV_CH_LAYOUT_3POINT1 (AV_CH_LAYOUT_SURROUND|AV_CH_LOW_FREQUENCY)
#define AV_CH_LAYOUT_4POINT0 (AV_CH_LAYOUT_SURROUND|AV_CH_BACK_CENTER)
#define AV_CH_LAYOUT_4POINT1 (AV_CH_LAYOUT_4POINT0|AV_CH_LOW_FREQUENCY)
#define AV_CH_LAYOUT_2_2 (AV_CH_LAYOUT_STEREO|AV_CH_SIDE_LEFT|AV_CH_SIDE_RIGHT)
#define AV_CH_LAYOUT_QUAD (AV_CH_LAYOUT_STEREO|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT)
#define AV_CH_LAYOUT_5POINT0 (AV_CH_LAYOUT_SURROUND|AV_CH_SIDE_LEFT|AV_CH_SIDE_RIGHT)
#define AV_CH_LAYOUT_5POINT1 (AV_CH_LAYOUT_5POINT0|AV_CH_LOW_FREQUENCY)
#define AV_CH_LAYOUT_5POINT0_BACK (AV_CH_LAYOUT_SURROUND|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT)
#define AV_CH_LAYOUT_5POINT1_BACK (AV_CH_LAYOUT_5POINT0_BACK|AV_CH_LOW_FREQUENCY)
#define AV_CH_LAYOUT_6POINT0 (AV_CH_LAYOUT_5POINT0|AV_CH_BACK_CENTER)
#define AV_CH_LAYOUT_6POINT0_FRONT (AV_CH_LAYOUT_2_2|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER)
#define AV_CH_LAYOUT_HEXAGONAL (AV_CH_LAYOUT_5POINT0_BACK|AV_CH_BACK_CENTER)
#define AV_CH_LAYOUT_6POINT1 (AV_CH_LAYOUT_5POINT1|AV_CH_BACK_CENTER)
#define AV_CH_LAYOUT_6POINT1_BACK (AV_CH_LAYOUT_5POINT1_BACK|AV_CH_BACK_CENTER)
#define AV_CH_LAYOUT_6POINT1_FRONT (AV_CH_LAYOUT_6POINT0_FRONT|AV_CH_LOW_FREQUENCY)
#define AV_CH_LAYOUT_7POINT0 (AV_CH_LAYOUT_5POINT0|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT)
#define AV_CH_LAYOUT_7POINT0_FRONT (AV_CH_LAYOUT_5POINT0|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER)
#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)
#define AV_CH_LAYOUT_OCTAGONAL (AV_CH_LAYOUT_5POINT0|AV_CH_BACK_LEFT|AV_CH_BACK_CENTER|AV_CH_BACK_RIGHT)
#define AV_CH_LAYOUT_HEXADECAGONAL (AV_CH_LAYOUT_OCTAGONAL|AV_CH_WIDE_LEFT|AV_CH_WIDE_RIGHT|AV_CH_TOP_BACK_LEFT|AV_CH_TOP_BACK_RIGHT|AV_CH_TOP_BACK_CENTER|AV_CH_TOP_FRONT_CENTER|AV_CH_TOP_FRONT_LEFT|AV_CH_TOP_FRONT_RIGHT)
#define AV_CH_LAYOUT_STEREO_DOWNMIX (AV_CH_STEREO_LEFT|AV_CH_STEREO_RIGHT)
AVMatrixEncoding(没看明白)
enum AVMatrixEncoding {
AV_MATRIX_ENCODING_NONE,
AV_MATRIX_ENCODING_DOLBY,
AV_MATRIX_ENCODING_DPLII,
AV_MATRIX_ENCODING_DPLIIX,
AV_MATRIX_ENCODING_DPLIIZ,
AV_MATRIX_ENCODING_DOLBYEX,
AV_MATRIX_ENCODING_DOLBYHEADPHONE,
AV_MATRIX_ENCODING_NB
};
chanel_names
struct channel_name {
const char *name;
const char *description;
};
static const struct channel_name channel_names[] = {
[0] = { "FL", "front left" },
[1] = { "FR", "front right" },
[2] = { "FC", "front center" },
[3] = { "LFE", "low frequency" },
[4] = { "BL", "back left" },
[5] = { "BR", "back right" },
[6] = { "FLC", "front left-of-center" },
[7] = { "FRC", "front right-of-center" },
[8] = { "BC", "back center" },
[9] = { "SL", "side left" },
[10] = { "SR", "side right" },
[11] = { "TC", "top center" },
[12] = { "TFL", "top front left" },
[13] = { "TFC", "top front center" },
[14] = { "TFR", "top front right" },
[15] = { "TBL", "top back left" },
[16] = { "TBC", "top back center" },
[17] = { "TBR", "top back right" },
[29] = { "DL", "downmix left" },
[30] = { "DR", "downmix right" },
[31] = { "WL", "wide left" },
[32] = { "WR", "wide right" },
[33] = { "SDL", "surround direct left" },
[34] = { "SDR", "surround direct right" },
[35] = { "LFE2", "low frequency 2" },
};
channel_layout_map
static const struct {
const char *name;
int nb_channels;
uint64_t layout;
} channel_layout_map[] = {
{ "mono", 1, AV_CH_LAYOUT_MONO },
{ "stereo", 2, AV_CH_LAYOUT_STEREO },
{ "2.1", 3, AV_CH_LAYOUT_2POINT1 },
{ "3.0", 3, AV_CH_LAYOUT_SURROUND },
{ "3.0(back)", 3, AV_CH_LAYOUT_2_1 },
{ "4.0", 4, AV_CH_LAYOUT_4POINT0 },
{ "quad", 4, AV_CH_LAYOUT_QUAD },
{ "quad(side)", 4, AV_CH_LAYOUT_2_2 },
{ "3.1", 4, AV_CH_LAYOUT_3POINT1 },
{ "5.0", 5, AV_CH_LAYOUT_5POINT0_BACK },
{ "5.0(side)", 5, AV_CH_LAYOUT_5POINT0 },
{ "4.1", 5, AV_CH_LAYOUT_4POINT1 },
{ "5.1", 6, AV_CH_LAYOUT_5POINT1_BACK },
{ "5.1(side)", 6, AV_CH_LAYOUT_5POINT1 },
{ "6.0", 6, AV_CH_LAYOUT_6POINT0 },
{ "6.0(front)", 6, AV_CH_LAYOUT_6POINT0_FRONT },
{ "hexagonal", 6, AV_CH_LAYOUT_HEXAGONAL },
{ "6.1", 7, AV_CH_LAYOUT_6POINT1 },
{ "6.1(back)", 7, AV_CH_LAYOUT_6POINT1_BACK },
{ "6.1(front)", 7, AV_CH_LAYOUT_6POINT1_FRONT },
{ "7.0", 7, AV_CH_LAYOUT_7POINT0 },
{ "7.0(front)", 7, AV_CH_LAYOUT_7POINT0_FRONT },
{ "7.1", 8, AV_CH_LAYOUT_7POINT1 },
{ "7.1(wide)", 8, AV_CH_LAYOUT_7POINT1_WIDE_BACK },
{ "7.1(wide-side)", 8, AV_CH_LAYOUT_7POINT1_WIDE },
{ "octagonal", 8, AV_CH_LAYOUT_OCTAGONAL },
{ "hexadecagonal", 16, AV_CH_LAYOUT_HEXADECAGONAL },
{ "downmix", 2, AV_CH_LAYOUT_STEREO_DOWNMIX, },
};
utilty functions
get_channel_name
- brief:利用通道id获取通道字符标示的名称
- parameter：channel_id
- return：通道的字符表示
static const char *get_channel_name(int channel_id)
{
if (channel_id < 0 || channel_id >= FF_ARRAY_ELEMS(channel_names))
return NULL;
return channel_names[channel_id].name;
}
av_get_default_channel_layout
- brief：利用通道数量获取默认的通道布局
/**
* Return default channel layout for a given number of channels.
*/
int64_t av_get_default_channel_layout(int nb_channels) {
int i;
for (i = 0; i < FF_ARRAY_ELEMS(channel_layout_map); i++)
if (nb_channels == channel_layout_map[i].nb_channels)
return channel_layout_map[i].layout;
return 0;
}
get_channel_layout_single
- brief：
static uint64_t get_channel_layout_single(const char *name, int name_len)
{
int i;
char *end;
int64_t layout;
for (i = 0; i < FF_ARRAY_ELEMS(channel_layout_map); i++) {
if (strlen(channel_layout_map[i].name) == name_len &&
!memcmp(channel_layout_map[i].name, name, name_len))
return channel_layout_map[i].layout;
}
for (i = 0; i < FF_ARRAY_ELEMS(channel_names); i++)
if (channel_names[i].name &&
strlen(channel_names[i].name) == name_len &&
!memcmp(channel_names[i].name, name, name_len))
return (int64_t)1 << i;
errno = 0;
i = strtol(name, &end, 10);
if (!errno && (end + 1 - name == name_len && *end == 'c'))
return av_get_default_channel_layout(i);
errno = 0;
layout = strtoll(name, &end, 0);
if (!errno && end - name == name_len)
return FFMAX(layout, 0);
return 0;
}
av_get_channel_layout
- bried：利用layout名称获取唯一id
- return：如果没匹配到返回0,否则返回layout_id
uint64_t av_get_channel_layout(const char *name){
}
/**
* Return a channel layout and the number of channels based on the specified name.
*
* This function is similar to (@see av_get_channel_layout), but can also parse
* unknown channel layout specifications.
*
* @param[in] name channel layout specification string
* @param[out] channel_layout parsed channel layout (0 if unknown)
* @param[out] nb_channels number of channels
*
* @return 0 on success, AVERROR(EINVAL) if the parsing fails.
*/
int av_get_extended_channel_layout(const char *name, uint64_t* channel_layout, int* nb_channels);
/**
* Return a description of a channel layout.
* If nb_channels is <= 0, it is guessed from the channel_layout.
*
* @param buf put here the string containing the channel layout
* @param buf_size size in bytes of the buffer
*/
void av_get_channel_layout_string(char *buf, int buf_size, int nb_channels, uint64_t channel_layout);
struct AVBPrint;
/**
* Append a description of a channel layout to a bprint buffer.
*/
void av_bprint_channel_layout(struct AVBPrint *bp, int nb_channels, uint64_t channel_layout);
/**
* Return the number of channels in the channel layout.
*/
int av_get_channel_layout_nb_channels(uint64_t channel_layout);
/**
* Return default channel layout for a given number of channels.
*/
int64_t av_get_default_channel_layout(int nb_channels);
/**
* Get the index of a channel in channel_layout.
*
* @param channel a channel layout describing exactly one channel which must be
* present in channel_layout.
*
* @return index of channel in channel_layout on success, a negative AVERROR
* on error.
*/
int av_get_channel_layout_channel_index(uint64_t channel_layout,
uint64_t channel);
/**
* Get the channel with the given index in channel_layout.
*/
uint64_t av_channel_layout_extract_channel(uint64_t channel_layout, int index);
/**
* Get the name of a given channel.
*
* @return channel name on success, NULL on error.
*/
const char *av_get_channel_name(uint64_t channel);
/**
* Get the description of a given channel.
*
* @param channel a channel layout with a single channel
* @return channel description on success, NULL on error
*/
const char *av_get_channel_description(uint64_t channel);
/**
* Get the value and name of a standard channel layout.
*
* @param[in] index index in an internal list, starting at 0
* @param[out] layout channel layout mask
* @param[out] name name of the layout
* @return 0 if the layout exists,
* <0 if index is beyond the limits
*/
int av_get_standard_channel_layout(unsigned index, uint64_t *layout,
const char **name);