[FFmpeg-devel] [PATCH v2] fftools/ffmpeg: add an option to forbid the fallback to software path when hardware init fails

[Eoff, Ullysses A]

> -----Original Message-----
> From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf Of Linjie Fu
> Sent: Thursday, November 08, 2018 7:14 PM
> To: ffmpeg-devel at ffmpeg.org
> Cc: Fu, Linjie <linjie.fu at intel.com>
> Subject: [FFmpeg-devel] [PATCH v2] fftools/ffmpeg: add an option to forbid the fallback to software path when hardware init fails
> 
> Currently ff_get_format will go through all usable choices if the chosen
> format was not supported. It will fallback to software path if the hardware
> init fails.
> 
> Provided an option "-fallback_forbid 1" in user-code to detect frame->format and
> hwaccel_get_buffer in get_buffer. If hardware init fails, returns an error.
> 

I'm not sure I like this option name ("-fallback_forbid").  How about "-disable_fallback",
"-hwaccel_or_die", "-require_hwaccel" or "-no_sw_fallback"?  I like the last two the most.
Or maybe someone has a better suggestion?

> Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> ---
> 
> [v2] detect hardware init failures in get_buffer and modify in user-code
> 
>  fftools/ffmpeg.c     | 2 ++
>  fftools/ffmpeg.h     | 1 +
>  fftools/ffmpeg_opt.c | 3 +++
>  3 files changed, 6 insertions(+)
> 
> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
> index da4259a9a8..45694fef57 100644
> --- a/fftools/ffmpeg.c
> +++ b/fftools/ffmpeg.c
> @@ -2890,6 +2890,8 @@ static int get_buffer(AVCodecContext *s, AVFrame *frame, int flags)
> 
>      if (ist->hwaccel_get_buffer && frame->format == ist->hwaccel_pix_fmt)
>          return ist->hwaccel_get_buffer(s, frame, flags);
> +    else if (ist->fallback_forbid)
> +        return AVERROR(EINVAL);
> 
>      return avcodec_default_get_buffer2(s, frame, flags);
>  }
> diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
> index eb1eaf6363..67ddaeaaee 100644
> --- a/fftools/ffmpeg.h
> +++ b/fftools/ffmpeg.h
> @@ -365,6 +365,7 @@ typedef struct InputStream {
>      enum AVHWDeviceType hwaccel_device_type;
>      char  *hwaccel_device;
>      enum AVPixelFormat hwaccel_output_format;
> +    int fallback_forbid;
> 
>      /* hwaccel context */
>      void  *hwaccel_ctx;
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index d4851a2cd8..314e25565c 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -3600,6 +3600,9 @@ const OptionDef options[] = {
>      { "autorotate",       HAS_ARG | OPT_BOOL | OPT_SPEC |
>                            OPT_EXPERT | OPT_INPUT,                                { .off = OFFSET(autorotate) },
>          "automatically insert correct rotate filters" },
> +    { "fallback_forbid",  HAS_ARG | OPT_BOOL | OPT_SPEC |
> +                          OPT_EXPERT | OPT_INPUT,                                { .off = OFFSET(fallback_forbid)},
> +      "forbid the fallback to default software path when hardware init fails"},
> 
>      /* audio options */
>      { "aframes",        OPT_AUDIO | HAS_ARG  | OPT_PERFILE | OPT_OUTPUT,           { .func_arg = opt_audio_frames },
> --
> 2.17.1
> 
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