[FFmpeg-devel] [PATCH] ffmpeg: default hwaccel_output_format to cuda when hwaccel is cuvid

[James Almer]

On 3/6/2020 7:42 PM, Timo Rothenpieler wrote:
> On 06.03.2020 23:39, James Almer wrote:
>> On 3/6/2020 7:35 PM, Timo Rothenpieler wrote:
>>> On 06.03.2020 23:17, James Almer wrote:
>>>> On 3/6/2020 11:45 AM, James Almer wrote:
>>>>> On 3/6/2020 10:35 AM, Timo Rothenpieler wrote:
>>>>>> This ensures old commandlines using -hwaccel cuvid don't break due to
>>>>>> the recent removal of the the cuvid-specific hwaccel bringup.
>>>>>> ---
>>>>>>    fftools/ffmpeg_opt.c | 26 ++++++++++++++------------
>>>>>>    1 file changed, 14 insertions(+), 12 deletions(-)
>>>>>>
>>>>>> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
>>>>>> index 1b721c4954..c8fe263730 100644
>>>>>> --- a/fftools/ffmpeg_opt.c
>>>>>> +++ b/fftools/ffmpeg_opt.c
>>>>>> @@ -816,6 +816,20 @@ static void add_input_streams(OptionsContext
>>>>>> *o, AVFormatContext *ic)
>>>>>>                ist->top_field_first = -1;
>>>>>>                MATCH_PER_STREAM_OPT(top_field_first, i,
>>>>>> ist->top_field_first, ic, st);
>>>>>>    +            MATCH_PER_STREAM_OPT(hwaccel_output_formats, str,
>>>>>> +                                 hwaccel_output_format, ic, st);
>>>>>> +            if (!hwaccel_output_format && hwaccel &&
>>>>>> !strcmp(hwaccel, "cuvid")) {
>>>>>
>>>>> Isn't hwaccel first set in the MATCH_PER_STREAM_OPT() call bellow?
>>>>
>>>> This change also needs both a code comment explaining why it's being
>>>> done, and a log message informing the CLI user a hardware pix_fmt is
>>>> forcefully being chosen for backwards compat reasons, that it's
>>>> deprecated behavior, and that it will stop working after a while.
>>>
>>> It can still be overridden by the user, but yeah, a deprecation warning
>>> is probably in order.
>>> For both cuvid and nvdec actually.
>>
>> nvdec didn't default to the cuda pixfmt, afaik, so not necessary for
>> that one. Or you mean you want to deprecate the nvdec alias and keep
>> only "cuda"?
> 
> Yes, as seen on recent github threads, the multitude of different
> -hwaccel names, which do the exact same thing, causes great confusion.

Not sure if removing the nvdec alias is a good idea, considering the
lavc hwaccels are called like that.
If i configure ffmpeg with --enable-nvdec --enable-hwaccel=hevc_nvdec,
expecting a command line like -hwaccel nvdec to work is not outlandish.

How about making sure cuvid is a term left exclusively for the relevant
lavc hardware decoders, and nvdec for the relevant lavc hwaccels?
Although I'm not sure how the hardware based filters play into this.