[pHash-support] Initial Testing

Evan Klinger eklinger at phash.org
Sat Jan 30 09:16:27 PST 2010


David,
How many hashes were found from the videos? From the original and from
the attacked version?
Thanks

On Sat, Jan 30, 2010 at 8:57 AM, Evan Klinger <eklinger at phash.org> wrote:
> David,
>
> How much resize, cropping and trimming are you talking about?
> We are aware of the performance issue and we are investigating ways to
> speed it up but at this time there is no getting around reading the
> video frame by frame.
> The video hash accepts any format that FFmpeg does, and it does
> support flv files. You may be missing the codec for FFmpeg. I played
> an FLV file last night using mplayer without any trouble.
> You can also try playing around with the video hash parameters to see
> if it helps when matching. Try adjusting the adaptive threshold lower
> in the source. You can also tweak the sample rate. Currently it is
> sampling every .5 second. Setting it to sample every second may help.
> Please let us know your findings.
>
> Thank you
> Evan
>
> On Sat, Jan 30, 2010 at 1:49 AM, David C <d140frv at hotmail.co.uk> wrote:
>> Hi,
>>
>> These are the results of the initial testing from my developer:
>>
>> I uploaded different types of codec, trimmed & resize version of 1 video on
>> the server. Upon testing, found out that video hash is not accurate yet. Its
>> working fine if the 2 video compared have same length/duration and
>> resolution. Buf if the video is resize, crop or trimmed, the phash get 0 in
>> similarity :(  which is not good and the process is too long coz its process
>> frame by frame. Video hash method doesn't accept flv files also. I've used
>> to test the existing test_video on the source file coz all functions for
>> video hash testing are their. So I conclude that it's not best to use the
>> video hash method. If you've doubt with my testing, you may ask someone to
>> thoroughly test the video hash. :)
>>
>> I am just confirming it is the variable length DCT.
>>
>> Thanks,
>>
>> David
>>
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>



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