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

["\"zhilizhao(赵志立)\"" <quinkblack@foxmail.com>]

> 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”

> 
> -- 
> Anton Khirnov
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