[FFmpeg-devel] [PATCH 2/5] vulkan_decode: use the new AVHWFramesContext.opaque field

[Lynne]

Jun 18, 2023, 13:10 by anton at khirnov.net:

> Quoting Lynne (2023-06-13 14:53:35)
>
>> Jun 13, 2023, 14:29 by anton at khirnov.net:
>>
>> > Quoting Lynne (2023-06-13 06:19:34)
>> >
>> >> This depends on the previous patch, and allows moving the codec
>> >> profile to the new AVHWFramesContext.opaque field.
>> >>
>> >> Patch attached.
>> >>
>> >>
>> >> From f992905250062711fab7522906a573ff8ab5f716 Mon Sep 17 00:00:00 2001
>> >> From: Lynne <dev at lynne.ee>
>> >> Date: Tue, 13 Jun 2023 06:10:20 +0200
>> >> Subject: [PATCH 2/5] vulkan_decode: use the new AVHWFramesContext.opaque field
>> >>
>> >> ---
>> >>  libavcodec/vulkan_decode.c | 56 +++++++++++++++++++++++---------------
>> >>  libavcodec/vulkan_decode.h |  6 ++--
>> >>  2 files changed, 37 insertions(+), 25 deletions(-)
>> >>
>> >
>> > This will not work, because the callers are not required to call
>> > avcodec_get_hw_frames_parameters() and can create the frames context
>> > themselves.
>> >
>>
>> Indeed they are. This commit doesn't break this.
>>
>>
>> > The decoder is then not allowed to make any assumptions about the opaque
>> > field.
>> >
>>
>> Exactly. This is just for the case that the user calls avcodec_get_hw_frames_parameters.
>> Then, we need somewhere to put the profile.
>> The opaque field is only set, it is never read in this particular case.
>> Since it's libavcodec creating the frames context in this case, and since the user
>> explicitly asked for frames parameters to be set, I don't think it's a problem
>> to set a public field, much the same way the width, height and sw_format
>> values are set.
>>
>> If the user doesn't call avcodec_get_hw_frames_parameters, the rest
>> of the code wouldn't notice. The rest of the decoder code gets the profile
>> via the create_pnext chain (where the pointers to the profile structs must be).
>> So users can attach their own profile, and store it wherever, including
>> the opaque field.
>>
>> This commit also fixes the situation where a users calls
>> avcodec_get_hw_frames_parameters, gets a frame parameters.
>> destroys the decode context, and uses the same frames context
>> which was created for another decoder.
>>
>
> Why can't you use the existing user_opaque field?
>

Didn't notice there was one.