[FFmpeg-devel] [PATCH 5/8] lavd: add device capabilities API

[Lukasz Marek]

On 10.04.2014 23:57, Don Moir wrote:
>
> ----- Original Message ----- From: "Lukasz Marek"
> <lukasz.m.luki2 at gmail.com>
> To: <ffmpeg-devel at ffmpeg.org>
> Sent: Thursday, April 10, 2014 4:34 PM
> Subject: Re: [FFmpeg-devel] [PATCH 5/8] lavd: add device capabilities API
>
>
>> On 10.04.2014 02:32, Don Moir wrote:
>>> Did you mean: by how or by now :)
>>>
>>> +typedef struct AVDeviceCapabilitiesQuery {
>>> +    const AVClass *class;
>>> +    AVFormatContext *device_context;
>>> +    enum AVCodecID codec;
>>> +    enum AVSampleFormat sample_format;
>>> +    enum AVPixelFormat pixel_format;
>>> +    int sample_rate;
>>> +    int channels;
>>> +    int64_t channel_layout;
>>> +    int window_width;
>>> +    int window_height;
>>> +    int frame_width;
>>> +    int frame_height;
>>> +    AVRational fps;
>>> +} AVDeviceCapabilitiesQuery;
>>>
>>> For a capture device and for each pixel format, width, and height, there
>>> can be a range of FPS values, like a min of a 1 FPS to max 60 FPS. Just
>>> varies for each device and format. So don't see how that fits into the
>>> AVDeviceCapabilitiesQuery structure as it stands.
>>
>> You query this structure, not use to store all possible values. Read
>> an example and doc, it is described.
>
> Not following thread very close so forgive is this is out of place. Ok
> you get device list and then what? Query every possible value? Maybe
> somewhere else and not seeing it. How many queries would I have to do to
> get all possible formats, widths, heights and frames rates that a device
> might support? I don't know.

4 queries. If they have dependencies than more, if you want to get all 
possible _valid_ combinations, but it depends on device and probably 
underlaying hardware to get exact number of queries.