Re: [FFmpeg-devel] [PATCH v2 1/3] avutil/hwcontext: add a function to get the AVHWDeviceType

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

"zhilizhao(赵志立)":
> 
> 
>> On Jun 30, 2022, at 4:43 PM, Anton Khirnov <anton@khirnov.net> wrote:
>>
>> Quoting Tong Wu (2022-06-30 04:45:56)
>>> Add a function to get the corresponding AVHWDeviceType from a given
>>> hardware pixel format.
>>>
>>> Signed-off-by: Tong Wu <tong1.wu@intel.com>
>>> ---
>>> libavutil/hwcontext.c | 12 ++++++++++++
>>> libavutil/hwcontext.h |  9 +++++++++
>>> 2 files changed, 21 insertions(+)
>>>
>>> diff --git a/libavutil/hwcontext.c b/libavutil/hwcontext.c
>>> index ab9ad3703e..3521ed34f4 100644
>>> --- a/libavutil/hwcontext.c
>>> +++ b/libavutil/hwcontext.c
>>> @@ -80,6 +80,18 @@ static const char *const hw_type_names[] = {
>>>     [AV_HWDEVICE_TYPE_VULKAN] = "vulkan",
>>> };
>>>
>>> +enum AVHWDeviceType av_hwdevice_get_type_by_pix_fmt(enum AVPixelFormat fmt)
>>> +{
>>> +    int i, j;
>>
>> Nit: you can and should declare loop indices in the loop statement
>> itself
>>
>>> +    for (i = 0; hw_table[i]; i++) {
>>> +        for (j = 0; hw_table[i]->pix_fmts[j] != AV_PIX_FMT_NONE; j++) {
>>> +            if (hw_table[i]->pix_fmts[j] == fmt)
>>> +                return hw_table[i]->type;
>>> +        }
>>> +    }
>>> +    return AV_HWDEVICE_TYPE_NONE;
>>> +}
>>> +
>>> enum AVHWDeviceType av_hwdevice_find_type_by_name(const char *name)
>>> {
>>>     int type;
>>> diff --git a/libavutil/hwcontext.h b/libavutil/hwcontext.h
>>> index c18b7e1e8b..97f94403e2 100644
>>> --- a/libavutil/hwcontext.h
>>> +++ b/libavutil/hwcontext.h
>>> @@ -229,6 +229,15 @@ typedef struct AVHWFramesContext {
>>>     int width, height;
>>> } AVHWFramesContext;
>>>
>>> +/**
>>> + * Get the device type by a given pixel format.
>>> + *
>>> + * @param fmt Pixel format from enum AVPixelFormat.
>>> + * @return The type from enum AVHWDeviceType, or AV_HWDEVICE_TYPE_NONE if
>>> + *         not found.
>>> + */
>>> +enum AVHWDeviceType av_hwdevice_get_type_by_pix_fmt(enum AVPixelFormat fmt);
>>
>> I wonder if we should consider the possibility of a format being
>> supported by more than one device type.
> 
> For future proof, we can make it clear that there is no guarantee
> that the device type is unique, e.g.,
> 
> "Get any device type which support the given pixel format”
> 

Then you'd need to return a list or modify the user accept an iterator.

- Andreas
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