[pHash-support] mpeg1 and mpeg2 codecs are partially working with pHash

[Evan Klinger]

Hi Pratik,

Unfortunately this is likely due to the key frame extraction algorithm used
in pHash GPL for the video hash. We do not have a fix for it at this time.

Thank you
Evan


On Wed, Oct 30, 2013 at 9:53 AM, Pratik Bhoir <pbhoir at blue-efficience.com>wrote:

> Hello pHash team,
>
> My company is searching for a video fingerprint technology to automate
> more our processes.
> Currently we are testing pHash open source for video hashing and depending
> on the results we might be interested in buying pHash Pro licence.
>
> We came across what looks like to be an issue that pHash is not
> calculating enough hash (only one hash value, irrespective of length of the
> video) values for
> mpeg1 and mpeg2 codecs.
>
> Brief description of the issue:
>
> System : Ubuntu 12.04 LTS
> phash 0.9.6 (configured only with --enable-shared option)
> CImg 1.4.9 (installed directly from Ubuntu repository)
> ffmpeg 2.1  (configured only with --enable-shared option)
>
> I have also tried all available versions of ffmpeg with the same result.
>
> Though I edited one file before testing video hash,
> 1. cimgffmpeg.cpp : I edited this file because initially I was getting
> segfault while executing test_video.
>                               I edited the function long
> GetNumberVideoFrames(const char *file) and float fps(const char *filename),
> in both functions I assigned AVformatContext *pFormatCtx = NULL; as
> mentioned in one of the support archive and it worked. URL:
> http://lists.phash.org/htdig.cgi/phash-support-phash.org/2013-January/000140.html
>
>
> Using the examples provided in pHash package, all the video coding formats
> that I have tested are working well except  mpeg1 and mpeg2.
> I have tried different videos with various lengths(5min, 20min and 45 min)
> but result is always one hash value for mpeg1 and mpeg2.
>
> Can you please look upon this issue and tell me where is the problem?
>
> Thank you for your time and help,
>
> - Pratik
>
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> pHash-support at lists.phash.org
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>
>
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