[FFmpeg-devel] [PATCH 07/17] swscale: add SWS_EXPERIMENTAL flag

[Niklas Haas]

On Sat, 26 Apr 2025 19:41:11 +0200 Niklas Haas <ffmpeg at haasn.xyz> wrote:
> From: Niklas Haas <git at haasn.dev>
>
> Give users and developers a way to opt in to the new format conversion code,
> and more code from the swscale rewrite in general.

This conflicts with the existing option "experimental" mapped to SWS_X
("experimental" scaler). So we need to find a new name for it.

I also propose that we deprecate SWS_X, perhaps alongside other obscure and
less useful options like a_dither and x_dither.

> ---
>  doc/APIchanges       | 3 +++
>  doc/scaler.texi      | 3 +++
>  libswscale/options.c | 1 +
>  libswscale/swscale.h | 7 +++++++
>  libswscale/version.h | 2 +-
>  5 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/doc/APIchanges b/doc/APIchanges
> index 22aa6fa5c7..84bc721569 100644
> --- a/doc/APIchanges
> +++ b/doc/APIchanges
> @@ -2,6 +2,9 @@ The last version increases of all libraries were on 2025-03-28
>
>  API changes, most recent first:
>
> +2025-04-xx - xxxxxxxxxx - lsws 9.1.100 - swscale.h
> +  Add SWS_EXPERIMENTAL flag.
> +
>  2025-04-16 - c818c67991 - libpostproc 59.1.100 - postprocess.h
>    Deprecate PP_CPU_CAPS_3DNOW.
>
> diff --git a/doc/scaler.texi b/doc/scaler.texi
> index eb045de6b7..519a83b5d3 100644
> --- a/doc/scaler.texi
> +++ b/doc/scaler.texi
> @@ -68,6 +68,9 @@ Select full chroma input.
>
>  @item bitexact
>  Enable bitexact output.
> +
> + at item experimental
> +Allow the use of experimental new code. For testing only.
>  @end table
>
>  @item srcw @var{(API only)}
> diff --git a/libswscale/options.c b/libswscale/options.c
> index feecae8c89..044c7c7f0b 100644
> --- a/libswscale/options.c
> +++ b/libswscale/options.c
> @@ -50,6 +50,7 @@ static const AVOption swscale_options[] = {
>          { "full_chroma_inp", "full chroma input",             0,  AV_OPT_TYPE_CONST, { .i64 = SWS_FULL_CHR_H_INP }, .flags = VE, .unit = "sws_flags" },
>          { "bitexact",        "bit-exact mode",                0,  AV_OPT_TYPE_CONST, { .i64 = SWS_BITEXACT       }, .flags = VE, .unit = "sws_flags" },
>          { "error_diffusion", "error diffusion dither",        0,  AV_OPT_TYPE_CONST, { .i64 = SWS_ERROR_DIFFUSION}, .flags = VE, .unit = "sws_flags" },
> +        { "experimental",    "allow experimental new code",   0,  AV_OPT_TYPE_CONST, { .i64 = SWS_EXPERIMENTAL   }, .flags = VE, .unit = "sws_flags" },
>
>      { "param0",          "scaler param 0", OFFSET(scaler_params[0]), AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  }, INT_MIN, INT_MAX, VE },
>      { "param1",          "scaler param 1", OFFSET(scaler_params[1]), AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  }, INT_MIN, INT_MAX, VE },
> diff --git a/libswscale/swscale.h b/libswscale/swscale.h
> index b04aa182d2..82a69e97fc 100644
> --- a/libswscale/swscale.h
> +++ b/libswscale/swscale.h
> @@ -155,6 +155,13 @@ typedef enum SwsFlags {
>      SWS_ACCURATE_RND   = 1 << 18,
>      SWS_BITEXACT       = 1 << 19,
>
> +    /**
> +     * Allow using experimental new code paths. This may be faster, slower,
> +     * or produce different output, with semantics subject to change at any
> +     * point in time. For testing and debugging purposes only.
> +     */
> +    SWS_EXPERIMENTAL   = 1 << 20,
> +
>      /**
>       * Deprecated flags.
>       */
> diff --git a/libswscale/version.h b/libswscale/version.h
> index 148efd83eb..4e54701aba 100644
> --- a/libswscale/version.h
> +++ b/libswscale/version.h
> @@ -28,7 +28,7 @@
>
>  #include "version_major.h"
>
> -#define LIBSWSCALE_VERSION_MINOR   0
> +#define LIBSWSCALE_VERSION_MINOR   1
>  #define LIBSWSCALE_VERSION_MICRO 100
>
>  #define LIBSWSCALE_VERSION_INT  AV_VERSION_INT(LIBSWSCALE_VERSION_MAJOR, \
> --
> 2.49.0
>