On 21/02/17 07:28, wm4 wrote:
> On Mon, 20 Feb 2017 21:54:03 +0000
> Mark Thompson <[email protected]> wrote:
>
>> On 20/02/17 05:37, wm4 wrote:
>>> On Sun, 19 Feb 2017 18:46:23 +0000
>>> Mark Thompson <[email protected]> wrote:
>>>
>>>> Creates a new device context from another of a different type which
>>>> refers to the same underlying hardware.
>>>> ---
>>>> libavutil/hwcontext.c | 78
>>>> ++++++++++++++++++++++++++++++++++++++++++
>>>> libavutil/hwcontext.h | 16 +++++++++
>>>> libavutil/hwcontext_internal.h | 8 +++++
>>>> 3 files changed, 102 insertions(+)
>>>>
>>>> diff --git a/libavutil/hwcontext.c b/libavutil/hwcontext.c
>>>> index 608da6872..1f9442622 100644
>>>> --- a/libavutil/hwcontext.c
>>>> +++ b/libavutil/hwcontext.c
>>>> @@ -65,6 +65,8 @@ static void hwdevice_ctx_free(void *opaque, uint8_t
>>>> *data)
>>>> if (ctx->free)
>>>> ctx->free(ctx);
>>>>
>>>> + av_buffer_unref(&ctx->internal->source_device);
>>>> +
>>>> av_freep(&ctx->hwctx);
>>>> av_freep(&ctx->internal->priv);
>>>> av_freep(&ctx->internal);
>>>> @@ -535,6 +537,82 @@ fail:
>>>> return ret;
>>>> }
>>>>
>>>> +int av_hwdevice_ctx_create_derived(AVBufferRef **dst_ref_ptr,
>>>> + enum AVHWDeviceType type,
>>>> + AVBufferRef *src_ref, int flags)
>>>> +{
>>>> + AVBufferRef *dst_ref = NULL, *tmp_ref;
>>>> + AVHWDeviceContext *dst_ctx, *src_ctx, *tmp_ctx;
>>>> + int ret = 0;
>>>> +
>>>> + src_ctx = (AVHWDeviceContext*)src_ref->data;
>>>> + if (src_ctx->type == type) {
>>>> + // Currently disallowed. It is possible that deriving a device of
>>>> + // the same type could do something useful (device partitioning?),
>>>> + // but for now just don't support it.
>>>> + return AVERROR(EINVAL);
>>>
>>> It could just be a no-nop (basically creating an alias). Whether that'd
>>> be useful, who knows.
>>
>> If you can come up with any case where that is useful, then sure. I
>> couldn't think of one, so making it always fail rather than doing something
>> unhelpful seemed reasonable.
>>
>
> It looks to me like this would be quite orthogonal. The user could call
> this function simply to create a new reference to a desired device
> type, without having to check whether src_ref is already the desired
> type (and having to call av_buffer_ref instead in this case).
Ok, I'm convinced: I'll change it to remove this check and make the loop below
start at the source device rather than its immediate parent.
>>>> + }
>>>> +
>>>> + // If the source device was originally derived from a device of the
>>>> + // target type (possibly through more intermediates), then return a
>>>> + // new reference to the original device.
>>>> + tmp_ref = src_ctx->internal->source_device;
>>>> + while (tmp_ref) {
>>>> + tmp_ctx = (AVHWDeviceContext*)tmp_ref->data;
>>>> + if (tmp_ctx->type == type) {
>>>> + dst_ref = av_buffer_ref(tmp_ref);
>>>> + if (!dst_ref) {
>>>> + ret = AVERROR(ENOMEM);
>>>> + goto fail;
>>>> + }
>>>> + goto done;
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