Identifying a video frame number or timestamp based on a source image?

[madwoota]

I have a few hundred video files (.TS) that I have recorded (Free-To-Air) that I would like to batch trim down to save some space. Similar to the concept of ComSkip for identifying commercial breaks for removal.

Ideally, I'd like to use a sample image as a source, then identify either the timestamp or frame number of the video file when that frame first appears in the video. This might be a high % based match given the variations in video codecs vs image formats. The actual source image would just be a grab from the opening title sequence of the show.

Once the start & end frame numbers are found, I can easily batch trim the files to the content between the markers.

I'm really just looking for some suggestions on methods, tools, applications, plugins, scripts or libraries I could utilise to do this as I'm stumped.

ComSkip couldn't match either the start or end of this particular show as there is no scene break or black sequence to segment it. It also incorrectly tags the start of the credits as the start of a commercial break.

OpenCV (via OpenFrameworks) seemed promising, but I'll need to teach myself C++ first and it doesnt handle .TS (although thats solvable with a quick transcode).

[StainlessS]

Google this:

A novel scheme for fast and efficient video sequence matching using compact signatures

White paper, identifying compressed frames.
Dont know if it is implemented in commercial or other software.

[madwoota]

Thanks StainlessS, I didnt actually read the paper, but some of the search results I got gave me a few hints to look again scene change detection. Specifically, this post (http://forum.doom9.org/showthread.php?t=170700) which pointed me at the Avisynth conditional & debug filters.

Turns out Avisynth has a Compare() function that outputs to a text file! Who knew? Lol.

It's a bit brute force, but I can make it work well enough for my needs. Just had to DGIndex the TS file to D2V then run the following Avisynth script:
LoadPlugin("dgdecode.dll")
clip1=MPEG2Source("test.d2v")

#This is in RGB24
clip2=ImageSource("snapshot.jpg", end=0, fps=25).ConvertToYV12()

Compare(clip1, clip2, "", "compare.log")

Process the subsequent compare.log and find the closest value to 0 in the Mean Deviation (frame #49)!
Mean Max Max
Absolute Mean Pos. Neg.
Frame Dev. Dev. Dev. Dev. PSNR (dB)
-----------------------------------------------------
45 51.9287 +35.2766 205 -59 11.8964
46 51.9408 +35.2722 207 -60 11.8930
47 51.9392 +35.2412 206 -60 11.8935
48 51.9580 +35.3230 209 -60 11.8908
49 1.2914 +0.0085 29 -16 41.8406
50 8.3169 -0.2046 149 -40 23.0569
51 12.8632 -0.4066 143 -45 20.3819
52 16.0608 -0.7585 140 -46 19.1283
53 18.4752 -0.9800 143 -47 18.2948


Appreciate the nudge in the right direction. Cheers.

[StainlessS]

Dont know if this of any use, MatchFrames and LocateFrames scripts: http://forum.doom9.org/showthread.php?t=164766&highlight=matchframes
Updates to both are included in RT_Stats zip.

For Searching for many frames in single clip, might want to take a peek at RT_QwikScan.
Slow to create a DBase for the target clip, but only milliseconds to find frames afterwards.

Edit: for scene change detection search 'dbsc' on forum.