[Libav-user] How to keep AVFrame data after codec close

Bruce Wheaton bruce at spearmorgan.com
Sun Dec 8 07:16:41 CET 2013

On Dec 6, 2013, at 4:39 PM, wm4 <nfxjfg at googlemail.com> wrote:

> On Thu, 5 Dec 2013 10:53:37 -0800
> Bruce Wheaton <bruce at spearmorgan.com> wrote:
>> On Dec 5, 2013, at 3:41 AM, Paul B Mahol <onemda at gmail.com> wrote:
>>> On 12/5/13, Eric Beuque <eric.beuque at gmail.com> wrote:
>>>> How i can tell libavcodec that i want to become the owner of the data and
>>>> be able to free it, to without codec context instance? I was thinking about
>>>> using get/release_buffer functions, but i don't know how to compute size of
>>>> the data.
>>>> Is data memcpy the only way to do this?
>>>> Note, that i also can't upgrade to new version of FFMPEG.
>>>> Thanks for your help.
>>> Use reference counting system.
>>> They you need to manually free frame once you will not need it
>>> (otherwise you leak memory), so you do not need to do copy.
>> In my recent experiments, it seemed that closing the codec actually frees all buffers, regardless of reference count. That makes sense - if the codec is gone, what would detect the decreased reference count? 
> Did you set AVCodecContext.refcounted_frames to 1? There are other
> weird requirements to use refcounting, such as allocating AVFrames with
> av_frame_alloc() instead of avcodec_frame_alloc() (or whatever it was).

Yes, I followed all the directions I could find, including those two. In the end, memory kept increasing, and I found that I couldn't keep buffers longer than i had the codec and context open.

It was also quite a memory hog. Saving the copy turned out to have some downsides.


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