Re: [FFmpeg-devel] [PATCH] vulkan_hevc: switch from a buffer pool to a simple malloc

[Lynne <dev@lynne.ee>]

Sep 15, 2023, 03:00 by andreas.rheinhardt@outlook.com:

> Lynne:
>
>> -static int get_data_set_buf(FFVulkanDecodeContext *s, AVBufferRef **data_buf,
>> -                            int nb_vps, AVBufferRef * const vps_list[HEVC_MAX_VPS_COUNT])
>> +static int alloc_hevc_header_structs(FFVulkanDecodeContext *s,
>> +                                     int nb_vps,
>> +                                     AVBufferRef * const vps_list[HEVC_MAX_VPS_COUNT])
>>  {
>> -    uint8_t *data_ptr;
>> +    uintptr_t data_ptr;
>>  HEVCHeaderSet *hdr;
>>  
>>  size_t base_size = sizeof(StdVideoH265SequenceParameterSet)*HEVC_MAX_SPS_COUNT +
>> @@ -93,22 +94,18 @@ static int get_data_set_buf(FFVulkanDecodeContext *s, AVBufferRef **data_buf,
>>  buf_size += sizeof(HEVCHeaderVPSSet)*vps->vps_num_hrd_parameters;
>>  }
>>  
>> -    if (buf_size > s->tmp_pool_ele_size) {
>> -        av_buffer_pool_uninit(&s->tmp_pool);
>> -        s->tmp_pool_ele_size = 0;
>> -        s->tmp_pool = av_buffer_pool_init(buf_size, NULL);
>> -        if (!s->tmp_pool)
>> +    if (buf_size > s->hevc_headers_size) {
>> +        av_freep(&s->hevc_headers);
>> +        s->hevc_headers_size = 0;
>> +        s->hevc_headers = av_mallocz(buf_size);
>>
>
> The earlier code did not zero-initialize the buffer. I thought the
> set_[vsp]ps functions were enough to initialize them.
>

Better to be on the safe side, in case I've forgotten to set a reserved
field (or better yet, I should remove references to them in case they're
renamed.


>> +        if (!s->hevc_headers)
>>  return AVERROR(ENOMEM);
>> -        s->tmp_pool_ele_size = buf_size;
>> +        s->hevc_headers_size = buf_size;
>>  }
>>  
>> -    *data_buf = av_buffer_pool_get(s->tmp_pool);
>> -    if (!(*data_buf))
>> -        return AVERROR(ENOMEM);
>> -
>>  /* Setup pointers */
>> -    data_ptr = (*data_buf)->data;
>> -    hdr = (HEVCHeaderSet *)data_ptr;
>> +    hdr = s->hevc_headers;
>> +    data_ptr = (uintptr_t)hdr;
>>  hdr->hvps = (HEVCHeaderVPS *)(data_ptr + base_size);
>>
>
> The standard way to get pointer that is at a certain byte offset from a
> given pointer is by casting said pointer to char* and applying the
> offset; casting to uintptr_t and back will work, but is actually not
> guaranteed. In fact, the whole data_ptr variable seems unnecessary.
> You may use FF_FIELD_AT from lavu/internal.h if you think that it is
> helpful for this. (I don't think so.)
>

Couldn't really think of a way to remove the data_ptr field.
Do you have any ideas? If not, I'll push this later today.
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