[FFmpeg-user] HEVC decoding of first frame

[Christian Herglotz]

Hello,

a) I know that there is some overhead. So I also tested this for 
sequences with different resolutions where I could observe the same 
behavior:

Mean decoding times for      FFmpeg        HM
     460*240 1 I-frame:             0.15s            0.18s
     460*240 2 I-frames:            0.23s            0.36s
     1920*1080 1 I-frame:         2.26s            2.89s
     1920*1080 2 I-frames:       3.43s            5.8s
     2560*1600 1 I-frame:         4.25s            5.46s
     2560*1600 2 I-frames:       6.43s            11s

A constant offset would not scale like this. Furthermore, I'm giving the 
corresponding decoding times for the HM-software as a reference where 
obviously the decoding time doubles for all cases.

b) The bit streams I am talking about are all-intra coded.

Thanks for your help!
Grüße zurück aus Franken!
Christian

Am 16.10.2015 um 11:37 schrieb Moritz Barsnick:
> On Thu, Oct 15, 2015 at 08:22:35 +0200, Christian Herglotz wrote:
>> When timing the process I found that the decoding of the
>> first frame always takes twice as long as the decoding of all the other
>> frames.
> I'm not sure I consider the test you provide as valid.
>
> a) Initializing a decoder has (some) overhead. That aligns your numbers
> a bit more.
>
> b) HEVC does not only consist of I-frames (unless you claim the
> opposite of your content). Who says P- or B-frames are easier/faster to
> decode than I-frames?
>
> That's just the theory from me. Someone who knows the code could help
> more, or someone who is willing to add the benchmarking macros into the
> code and rebuild. :-)
>
> Cheers,
> Gruß nach Franken,
> Moritz
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-- 
Dipl.-Ing. Dipl.-Wirt.Ing. Christian Herglotz

Chair of Multimedia Communications and Signal Processing
Friedrich-Alexander University Erlangen-Nürnberg
Cauerstr. 7, D-91058 Erlangen, Germany