Re: [FFmpeg-devel] [PATCH 06/10] lavc/videotoolboxenc: vastly simplify get_cv_pixel_info

From: Rick Kern <kernrj@gmail.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 06/10] lavc/videotoolboxenc: vastly simplify get_cv_pixel_info
Date: Sun, 19 Dec 2021 11:25:58 -0500
Message-ID: <CABmg8gWaUsyQSVvEDTQoMDgjvPgg-jO5+XMr4+8hV-VFgMXrww@mail.gmail.com> (raw)
In-Reply-To: <20211217001215.75135-7-rcombs@rcombs.me>

On Thu, Dec 16, 2021 at 7:13 PM rcombs <rcombs@rcombs.me> wrote:

> No longer requires per-format switch cases.
>
> The frame==0 path was unused (and would've crashed anyway).
> ---
>  libavcodec/videotoolboxenc.c | 69 +++++++-----------------------------
>  1 file changed, 13 insertions(+), 56 deletions(-)
>
> diff --git a/libavcodec/videotoolboxenc.c b/libavcodec/videotoolboxenc.c
> index b66d44f6b7..82e01fbe29 100644
> --- a/libavcodec/videotoolboxenc.c
> +++ b/libavcodec/videotoolboxenc.c
> @@ -2034,6 +2034,7 @@ static int get_cv_pixel_info(
>      size_t         *strides,
>      size_t         *contiguous_buf_size)
>  {
> +    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
>      VTEncContext *vtctx = avctx->priv_data;
>      int av_format       = frame->format;
>      int av_color_range  = frame->color_range;
> @@ -2041,6 +2042,9 @@ static int get_cv_pixel_info(
>      int range_guessed;
>      int status;
>
> +    if (!desc)
> +        return AVERROR(EINVAL);
> +
>      status = get_cv_pixel_format(avctx, av_format, av_color_range, color,
> &range_guessed);
>      if (status) {
>          av_log(avctx,
> @@ -2065,63 +2069,16 @@ static int get_cv_pixel_info(
>          }
>      }
>
> -    switch (av_format) {
> -    case AV_PIX_FMT_NV12:
> -        *plane_count = 2;
> -
> -        widths [0] = avctx->width;
> -        heights[0] = avctx->height;
> -        strides[0] = frame ? frame->linesize[0] : avctx->width;
> -
> -        widths [1] = (avctx->width  + 1) / 2;
> -        heights[1] = (avctx->height + 1) / 2;
> -        strides[1] = frame ? frame->linesize[1] : (avctx->width + 1) & -2;
> -        break;
> -
> -    case AV_PIX_FMT_YUV420P:
> -        *plane_count = 3;
> -
> -        widths [0] = avctx->width;
> -        heights[0] = avctx->height;
> -        strides[0] = frame ? frame->linesize[0] : avctx->width;
> -
> -        widths [1] = (avctx->width  + 1) / 2;
> -        heights[1] = (avctx->height + 1) / 2;
> -        strides[1] = frame ? frame->linesize[1] : (avctx->width + 1) / 2;
> -
> -        widths [2] = (avctx->width  + 1) / 2;
> -        heights[2] = (avctx->height + 1) / 2;
> -        strides[2] = frame ? frame->linesize[2] : (avctx->width + 1) / 2;
> -        break;
> +    *plane_count = av_pix_fmt_count_planes(avctx->pix_fmt);
>
> -    case AV_PIX_FMT_BGRA:
> -        *plane_count = 1;
> -
> -        widths [0] = avctx->width;
> -        heights[0] = avctx->height;
> -        strides[0] = frame ? frame->linesize[0] : avctx->width * 4;
> -        break;
> -
> -    case AV_PIX_FMT_P010LE:
> -        *plane_count = 2;
> -        widths[0] = avctx->width;
> -        heights[0] = avctx->height;
> -        strides[0] = frame ? frame->linesize[0] : (avctx->width * 2 + 63)
> & -64;
> -
> -        widths[1] = (avctx->width + 1) / 2;
> -        heights[1] = (avctx->height + 1) / 2;
> -        strides[1] = frame ? frame->linesize[1] : ((avctx->width + 1) / 2
> + 63) & -64;
> -        break;
> -
> -    default:
> -        av_log(
> -               avctx,
> -               AV_LOG_ERROR,
> -               "Could not get frame format info for color %d range %d.\n",
> -               av_format,
> -               av_color_range);
> -
> -        return AVERROR(EINVAL);
> +    for (i = 0; i < desc->nb_components; i++) {
> +        int p = desc->comp[i].plane;
> +        int chroma = (p != 0) && (!(desc->flags & AV_PIX_FMT_FLAG_ALPHA)
> || p + 1 != *plane_count);
>
This could be broken out into more variables to make the logic clearer. It
took me a while to parse this.

> +        int shiftw = chroma ? desc->log2_chroma_w : 0;
> +        int shifth = chroma ? desc->log2_chroma_h : 0;
> +        widths[p]  = (avctx->width  + ((1 << shiftw) >> 1)) >> shiftw;
> +        heights[p] = (avctx->height + ((1 << shifth) >> 1)) >> shifth;
> +        strides[p] = frame->linesize[p];
>      }
>
>      *contiguous_buf_size = 0;
> --
> 2.33.1
>
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