[FFmpeg-devel] libavcodec memory usage

[Matthieu Beghin]

Hi,

> On 03 Jan 2017, at 18:26, Ronald S. Bultje <rsbultje at gmail.com> wrote:
> 
> Hi,
> 
> On Tue, Jan 3, 2017 at 12:16 PM, Matthieu Beghin <
> matthieu.beghin at garagecube.com> wrote:
> 
>> 
>>> On 03 Jan 2017, at 17:55, Ronald S. Bultje <rsbultje at gmail.com> wrote:
>>> 
>>> Hi,
>>> 
>>> On Tue, Jan 3, 2017 at 11:44 AM, Matthieu Beghin <
>>> matthieu.beghin at garagecube.com> wrote:
>>> 
>>>>> I'm assuming that you're talking about 8K H264 with pixfmt=yuv420p10?
>> 8K
>>>> yuv420p10 frames are 100MB
>>>> 
>>>> Correct
>>>> 
>>>>> 32 plus delayed output and current_pic gives H264_MAX_PICTURE_COUNT =
>> 36
>>>> without threading: 36*100=3.6GB.
>>>> 
>>>> What do you mean by "delayed output” ? Can you link me to a document ?
>>> 
>>> 
>>> Out-of-order coded P-frames, they are buffered internally but not counted
>>> (and thus extra) on top of the max_refs value. I believe the spec calls
>>> this dpb (delayed pic buffer).
>>> 
>>>> Or maybe consider ditching 32bit support?
>>>> 
>>>> Unfortunately, that’s 10 years old app using OSX Carbon library (not 64
>>>> bits), and rewriting that part would be too much work.
>>>> 
>>> 
>>> I'm frowning at you. Really badly.
>>> 
>>> As an alternative, is there a way to know how much bytes are buffered ?
>>>> Iterating buffered frames ?
>>> 
>>> 
>>> What are you hoping to accomplish by knowing how many bytes are buffered?
>>> It doesn't solve the problem? But anyway, check
>>> H264Context->short/long_ref[]; delayed_pic[] gives you the delayed
>> output.
>>> 
>> 
>> I’m trying to let people use 8k movies if it will fit, but in case it
>> would use more than 1 GB, refuse to load the file. My application is a live
>> application, it cannot crash, and actually, it can...
>> 
>> So to know how much bytes livavcodec is using, I have to know the number
>> of frames / field, if it is interlaced and the number of delayed frames,
>> that's correct ?
>> 
>> How can I know the number of frames / field ?
>> To know if it’s interlaced: AVFrame::interlaced_frame
>> Number of delayed frames ?
>> 
>> Another solution is to start playing the movie and to check the buffered
>> data amount each time I decode a frame, then stop the movie if it uses more
>> than 1 GB...
>> In this case, just iterating H264Context->short/long_ref[]; delayed_pic[]
>> would be enough ?
>> How can I get the H264Context ?
> 
> 
> You can't access H264Context outside libavcodec without hacks...
> 
> Does something in libavcodec crash if you use too much mem? (If so: what?
> We want to fix this...) Or something else?

I’m generally blocked by crashes in Apple nVidia GL driver. When I’m not blocked by my own assertions (I should use a macro…) but anyway if the GL driver calls crash I can’t reach memory limit.

> The idea is that on OOM, libavcodec mallocs fail and we return gracefully.
> If that doesn't happen, we want to fix it.

If I have any crash in FFMPEG when reaching memory limit, I’ll document it and send you the info.

> Ronald
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