[FFmpeg-devel] [PATCH] avfilter: add ambisonic decoder filter

[James Almer]

On 10/30/2022 12:34 PM, Paul B Mahol wrote:
> +static const struct {
> +    const int              order;
> +    const int              inputs;
> +    const int              speakers;
> +    const int              near_field;
> +    const int              type;
> +    const double           xover;
> +    const AVChannelLayout  outlayout;
> +    const double          *speakers_azimuth;
> +    const double          *speakers_elevation;
> +    const double          *speakers_distance;
> +} ambisonic_tab[] = {
> +    [MONO] = {
> +        .order = 0,
> +        .inputs = 1,
> +        .speakers = 1,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO,
> +        .speakers_azimuth = (const double[1]){ 0. },
> +        .speakers_distance = (const double[1]){ 1. },
> +    },
> +    [STEREO] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 2,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO,
> +        .speakers_azimuth = (const double[2]){ -30, 30},
> +        .speakers_distance = same_distance,
> +    },
> +    [STEREO_DOWNMIX] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 2,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO_DOWNMIX,
> +        .speakers_azimuth = (const double[2]){ -90, 90 },
> +        .speakers_distance = same_distance,
> +    },
> +    [SURROUND] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 3,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_SURROUND,
> +        .speakers_azimuth = (const double[3]){ -45, 45, 0 },
> +        .speakers_distance = same_distance,
> +    },
> +    [L2_1] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 3,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_2_1,
> +        .speakers_azimuth = (const double[3]){ -45, 45, 180 },
> +        .speakers_distance = same_distance,
> +    },
> +    [TRIANGLE] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 3,
> +        .type = 1,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_SURROUND,
> +        .speakers_azimuth = (const double[3]){ -120, 120, 0 },
> +        .speakers_distance = same_distance,
> +    },
> +    [QUAD] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 4,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_QUAD,
> +        .speakers_azimuth = (const double[4]){ -45, 45, -135, 135 },
> +        .speakers_distance = same_distance,
> +    },
> +    [SQUARE] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 4,
> +        .type = 1,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_4POINT0,
> +        .speakers_azimuth = (const double[4]){ 0, -90, 180, 90 },
> +        .speakers_distance = same_distance,
> +    },
> +    [L4_0] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 4,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_4POINT0,
> +        .speakers_azimuth = (const double[4]){ -30, 30, 0, 180 },
> +        .speakers_distance = same_distance,
> +    },
> +    [L5_0] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 5,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_5POINT0_BACK,
> +        .speakers_azimuth = (const double[5]){ -30, 30, 0, -145, 145 },
> +        .speakers_distance = same_distance,
> +    },
> +    [L5_0_SIDE] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 5,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_5POINT0,
> +        .speakers_azimuth = (const double[5]){ -30, 30, 0, -110, 110 },
> +        .speakers_distance = same_distance,
> +    },
> +    [L6_0] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 6,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_6POINT0,
> +        .speakers_azimuth = (const double[6]){ -30, 30, 0, 180, -110, 110 },
> +        .speakers_distance = same_distance,
> +    },
> +    [L7_0] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 7,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_7POINT0,
> +        .speakers_azimuth = (const double[7]){ -30, 30, 0, -145, 145, -110, 110 },
> +        .speakers_distance = same_distance,
> +    },
> +    [TETRA] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 4,
> +        .type = 2,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_QUAD,
> +        .speakers_azimuth = (const double[4]){ -90, 90, 0, 180 },
> +        .speakers_elevation = (const double[4]){ -35.3, -35.3, 35.3, 35.3 },
> +        .speakers_distance = same_distance,
> +    },
> +    [CUBE] = {
> +        .order = 1,
> +        .inputs = 4,
> +        .speakers = 8,
> +        .type = 2,
> +        .near_field = NF_NONE,
> +        .xover = 0.,
> +        .outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_7POINT1,

7.1 defines an LFE channel, which is clearly not intended here, so it 
should be either:

.outlayout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MASK(8,
                  AV_CH_LAYOUT_QUAD     |
                  AV_CH_TOP_FRONT_LEFT  |
                  AV_CH_TOP_FRONT_RIGHT |
                  AV_CH_TOP_BACK_LEFT   |
                  AV_CH_TOP_BACK_RIGHT),

Or the AV_CHANNEL_LAYOUT_CUBE layout (using the exact same bitmask as 
above) after the patch i sent just now is committed.

> +        .speakers_azimuth = cube_azimuth,
> +        .speakers_elevation = cube_elevation,
> +        .speakers_distance = same_distance,
> +    },