VOD downloads "Crop Video" function is broken

[Nutri626]

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• [X] I have checked the issue page for duplicates
• [X] I am running the latest version (download here)

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since latest update of the program vod download is bugged, for example you cant normally download 3 second clip if you want to, for 7-8 second clip it only downloads 1 second, another bug is that start and end time function is not working well, it randomly cuts last 4-5 second and adds first 2-3 second when in the past it downloaded exact part it that you wanted, clearly something is broken about crop function

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[vaindil]

I'm looking at this right now. The problem is with the calculation of startOffsetSeconds on these lines: https://github.com/lay295/TwitchDownloader/blob/e48a04b2dd07c089cec63380c9814af17a4f36f4/TwitchDownloaderCore/VideoDownloader.cs#L87-L91

For debugging, I'm using VOD ID 2023900250 with times from 2:00:03 to 2:00:33.

Lines 87-89 get the initial offset location by calculating the total duration of all parts of the stream leading up to the one that was requested. In my example, this is 7200. Line 91 then subtracts CropBeginningTime from that, which is 7203 for me, so the final value is -3, and that's being passed into ffmpeg later on.

I think the fix should be changing line 91 to this, as CropBeginningTime will always be later than startOffsetSeconds. I'll open a PR shortly.

startOffsetSeconds = downloadOptions.CropBeginningTime - startOffsetSeconds;

[ScrubN]

I think the fix should be changing line 91 to this, as CropBeginningTime will always be later than startOffsetSeconds. I'll open a PR shortly.

startOffsetSeconds = downloadOptions.CropBeginningTime - startOffsetSeconds;

Whoops. If this line change fixes it, then I will merge.

[ScrubN]

No, it should be

startOffsetSeconds += (downloadOptions.CropBeginningTime - startOffsetSeconds)

[ScrubN]

No, it should be

startOffsetSeconds += (downloadOptions.CropBeginningTime - startOffsetSeconds)

I think the code is overcomplicated and we can just use downloadOptions.CropBeginningTime instead of adding segments?

[ScrubN]

I think the code is overcomplicated and we can just use downloadOptions.CropBeginningTime instead of adding segments?

This is wrong.

startOffsetSeconds = downloadOptions.CropBeginningTime - startOffsetSeconds;

This is right.

I didn't get enough sleep last night :/

[vaindil]

No, it should be

startOffsetSeconds += (downloadOptions.CropBeginningTime - startOffsetSeconds)

I think the code is overcomplicated and we can just use downloadOptions.CropBeginningTime instead of adding segments?

downloadOptions.CropBeginningTime is the number of seconds from the beginning of the VOD to start at; in my example it's 7203. That can't be passed directly into ffmpeg, because ffmpeg needs the time from the start of our specific clip. The only way to get that is by adding up all of the chunks before the current one to know how the offset 7203 relates to the start of the first chunk that was actually downloaded.

Similar info is already calculated by GetStreamListCrop, so in the future this could possibly be refactored a bit, but for a quick fix I think we need what I put.