Re: [FFmpeg-devel] [PATCH 14/17] avcodec/mlpenc: Simplify channel layout comparisons

[Paul B Mahol <onemda@gmail.com>]

On 9/18/22, Andreas Rheinhardt <andreas.rheinhardt@outlook.com> wrote:
> These encoders have AVCodec.ch_layouts set, so ff_encode_preinit()
> has already checked that the used channel layout is equivalent
> to one of these native layouts. Therefore one can simply
> compare the channel masks (with the added complication
> that one has to use av_channel_layout_subset() to get it,
> because the channel layout is not guaranteed to have
> AV_CHANNEL_ORDER_NATIVE).
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
>  libavcodec/mlpenc.c | 30 ++++++++++++++----------------
>  1 file changed, 14 insertions(+), 16 deletions(-)
>


probably ok

> diff --git a/libavcodec/mlpenc.c b/libavcodec/mlpenc.c
> index 463332593f..d2e28888f7 100644
> --- a/libavcodec/mlpenc.c
> +++ b/libavcodec/mlpenc.c
> @@ -480,6 +480,7 @@ static av_cold int mlp_encode_init(AVCodecContext
> *avctx)
>      static AVOnce init_static_once = AV_ONCE_INIT;
>      MLPEncodeContext *ctx = avctx->priv_data;
>      RestartHeader *const rh = &ctx->restart_header;
> +    uint64_t channels_present;
>      unsigned int sum = 0;
>      size_t size;
>      int ret;
> @@ -589,19 +590,20 @@ static av_cold int mlp_encode_init(AVCodecContext
> *avctx)
>
>      ctx->num_substreams = 1; // TODO: change this after adding
> multi-channel support for TrueHD
>
> +    channels_present = av_channel_layout_subset(&avctx->ch_layout,
> ~(uint64_t)0);
>      if (ctx->avctx->codec_id == AV_CODEC_ID_MLP) {
> -        static const AVChannelLayout layout_arrangement[] = {
> -            AV_CHANNEL_LAYOUT_MONO,         AV_CHANNEL_LAYOUT_STEREO,
> -            AV_CHANNEL_LAYOUT_2_1,          AV_CHANNEL_LAYOUT_QUAD,
> -            AV_CHANNEL_LAYOUT_2POINT1,      { 0 }, { 0 },
> -            AV_CHANNEL_LAYOUT_SURROUND,     AV_CHANNEL_LAYOUT_4POINT0,
> -            AV_CHANNEL_LAYOUT_5POINT0_BACK, AV_CHANNEL_LAYOUT_3POINT1,
> -            AV_CHANNEL_LAYOUT_4POINT1,
> AV_CHANNEL_LAYOUT_5POINT1_BACK,
> +        static const uint64_t layout_arrangement[] = {
> +            AV_CH_LAYOUT_MONO,         AV_CH_LAYOUT_STEREO,
> +            AV_CH_LAYOUT_2_1,          AV_CH_LAYOUT_QUAD,
> +            AV_CH_LAYOUT_2POINT1,      0, 0,
> +            AV_CH_LAYOUT_SURROUND,     AV_CH_LAYOUT_4POINT0,
> +            AV_CH_LAYOUT_5POINT0_BACK, AV_CH_LAYOUT_3POINT1,
> +            AV_CH_LAYOUT_4POINT1,      AV_CH_LAYOUT_5POINT1_BACK,
>          };
>          int i;
>
>          for (i = 0; i < FF_ARRAY_ELEMS(layout_arrangement); i++)
> -            if (!av_channel_layout_compare(&avctx->ch_layout,
> &layout_arrangement[i]))
> +            if (channels_present == layout_arrangement[i])
>                  break;
>          if (i == FF_ARRAY_ELEMS(layout_arrangement)) {
>              av_log(avctx, AV_LOG_ERROR, "Unsupported channel
> arrangement\n");
> @@ -613,29 +615,25 @@ static av_cold int mlp_encode_init(AVCodecContext
> *avctx)
>          ctx->summary_info      =
> ff_mlp_ch_info[ctx->channel_arrangement].summary_info     ;
>      } else {
>          /* TrueHD */
> -        if (!av_channel_layout_compare(&avctx->ch_layout,
> -
> &(AVChannelLayout)AV_CHANNEL_LAYOUT_MONO)) {
> +        if (channels_present == AV_CH_LAYOUT_MONO) {
>              ctx->ch_modifier_thd0    = 3;
>              ctx->ch_modifier_thd1    = 3;
>              ctx->ch_modifier_thd2    = 3;
>              ctx->channel_arrangement = 2;
>              ctx->thd_substream_info  = 0x14;
> -        } else if (!av_channel_layout_compare(&avctx->ch_layout,
> -
> &(AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO)) {
> +        } else if (channels_present == AV_CH_LAYOUT_STEREO) {
>              ctx->ch_modifier_thd0    = 1;
>              ctx->ch_modifier_thd1    = 1;
>              ctx->ch_modifier_thd2    = 1;
>              ctx->channel_arrangement = 1;
>              ctx->thd_substream_info  = 0x14;
> -        } else if (!av_channel_layout_compare(&avctx->ch_layout,
> -
> &(AVChannelLayout)AV_CHANNEL_LAYOUT_5POINT0)) {
> +        } else if (channels_present == AV_CH_LAYOUT_5POINT0) {
>              ctx->ch_modifier_thd0    = 1;
>              ctx->ch_modifier_thd1    = 1;
>              ctx->ch_modifier_thd2    = 1;
>              ctx->channel_arrangement = 11;
>              ctx->thd_substream_info  = 0x104;
> -        } else if (!av_channel_layout_compare(&avctx->ch_layout,
> -
> &(AVChannelLayout)AV_CHANNEL_LAYOUT_5POINT1)) {
> +        } else if (channels_present == AV_CH_LAYOUT_5POINT1) {
>              ctx->ch_modifier_thd0    = 2;
>              ctx->ch_modifier_thd1    = 1;
>              ctx->ch_modifier_thd2    = 2;
> --
> 2.34.1
>
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