[FFmpeg-devel] GSoC

Mark Thompson sw at jkqxz.net
Wed Mar 7 23:57:01 EET 2018

On 07/03/18 03:56, Dylan Fernando wrote:
> Thanks, it works now
> Would trying to implement an OpenCL version of vf_fade be a good idea for a
> qualification task, or would it be a better idea to try a different filter?

That sounds like a sensible choice to me, though if you haven't written a filter before you might find it helpful to write something simpler first to understand how it fits together (for example: vflip, which has trivial processing parts but still needs the surrounding boilerplate).

- Mark

(PS: be aware that top-posting is generally frowned upon on this mailing list.)

> On Wed, Mar 7, 2018 at 1:20 AM, Mark Thompson <sw at jkqxz.net> wrote:
>> On 06/03/18 12:37, Dylan Fernando wrote:
>>> Hi,
>>> I am Dylan Fernando. I am a Computer Science student from Australia. I am
>>> new to FFmpeg and I wish to apply for GSoC this year.
>>> I would like to do the Video filtering with OpenCL project and I have a
>> few
>>> questions. Would trying to implement an opencl version of vf_fade be a
>> good
>>> idea for the qualification task, or would I be better off using a
>> different
>>> filter?
>>> Also, I’m having a bit of trouble with running unsharp_opencl. I tried
>>> running:
>>> ffmpeg -hide_banner -nostats -v verbose -init_hw_device opencl=ocl:0.1
>>> -filter_hw_device ocl -i space.mpg -filter_complex unsharp_opencl
>> output.mp4
>>> but I got the error:
>>> [AVHWDeviceContext @ 0x7fdac050c700] 0.1: Apple / Intel(R) Iris(TM)
>>> Graphics 6100
>>> [mpeg @ 0x7fdac3132600] max_analyze_duration 5000000 reached at 5005000
>>> microseconds st:0
>>> Input #0, mpeg, from 'space.mpg':
>>>   Duration: 00:00:21.99, start: 0.387500, bitrate: 6108 kb/s
>>>     Stream #0:0[0x1e0]: Video: mpeg2video (Main), 1 reference frame,
>>> yuv420p(tv, bt470bg, bottom first, left), 720x480 [SAR 8:9 DAR 4:3], 6000
>>> kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
>>> Stream mapping:
>>>   Stream #0:0 (mpeg2video) -> unsharp_opencl
>>>   unsharp_opencl -> Stream #0:0 (mpeg4)
>>> Press [q] to stop, [?] for help
>>> [graph 0 input from stream 0:0 @ 0x7fdac0418800] w:720 h:480
>> pixfmt:yuv420p
>>> tb:1/90000 fr:30000/1001 sar:8/9 sws_param:flags=2
>>> [auto_scaler_0 @ 0x7fdac05232c0] w:iw h:ih flags:'bilinear' interl:0
>>> [Parsed_unsharp_opencl_0 @ 0x7fdac0715a80] auto-inserting filter
>>> 'auto_scaler_0' between the filter 'graph 0 input from stream 0:0' and
>> the
>>> filter 'Parsed_unsharp_opencl_0'
>>> Impossible to convert between the formats supported by the filter 'graph
>> 0
>>> input from stream 0:0' and the filter 'auto_scaler_0'
>>> Error reinitializing filters!
>>> Failed to inject frame into filter network: Function not implemented
>>> Error while processing the decoded data for stream #0:0
>>> Conversion failed!
>>> How do I correctly run unsharp_opencl? Should I be running it on a
>>> different video file?
>> It's intended to be used in filter graphs where much of the activity is
>> already happening on the GPU, so the input and output are in the
>> AV_PIX_FMT_OPENCL format which contains GPU-side OpenCL images.
>> If you want to use it standalone then you need hwupload and hwdownload
>> filters to move the frames between the CPU and GPU.  For your example, it
>> should work with:
>> ffmpeg -init_hw_device opencl=ocl:0.1 -filter_hw_device ocl -i space.mpg
>> -filter_complex hwupload,unsharp_opencl,hwdownload output.mp4
>> (There are constraints on what formats can be used and therefore suitable
>> files (or required format conversions), but I believe a normal yuv420p
>> video like this should work in all cases.)
>> - Mark

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