"Video Pass thru" ?

General questions or discussion about HandBrake, Video and/or audio transcoding, trends etc.
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dvdcollector
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"Video Pass thru" ?

Post by dvdcollector »

Description of problem or question:
Similar to being able to select* "audio pass through", which I frequently use for sources with HQ audio that shall not be mangled, I was wondering, is there also a way to pass thru the video and just do something to the audio? I have some material where it'd be a waste of time, processing and it's needless to numerically alter the video data for no good purpose - I just want to remove some languages from a multi language mkv or/and change the default language, etc. Can this be done?
From looking at the options in the video tab, it's not obvious so far.


* btw, I recently installed Handbrake on someone else's computer and "auto pass thru" was gone from the audio menu? What's up with that? I have not updated in a while on my machine, and this makes me want to note to never update again.

Steps to reproduce the problem (If Applicable):




HandBrake version (e.g., 1.0.0):

1.3


Operating system and version (e.g., Ubuntu 16.04 LTS, macOS 10.13 High Sierra, Windows 10 Creators Update):




HandBrake Activity Log ***required*** (see How-to get an activity log)

Does this default template make zero sense for this subforum, or am I misunderstanding its purpose?

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mduell
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Re: "Video Pass thru" ?

Post by mduell »

Not with HB; HB is a video transcoder.
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s55
HandBrake Team
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Re: "Video Pass thru" ?

Post by s55 »

Auto Passhthru is not gone from Audio.

Audio Passthru options only show if they are available now. I.e DTS Passthru won't show on an AC3 source audio track.
Previous versions did not hide incompatible options and users did not realise the fallback encoder was being used.

Also note, Auto Passhtru is only available on the Selection Behaviours screen as that's where the rules are setup for the track selection and configuration.

Having "Auto Passthru" on the main tab is very unclear as you as a user, have no idea what it's going to do unless you happen to know what HandBrake's capabilities are. Many got caught out by this.
Silent_Strider
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Re: "Video Pass thru" ?

Post by Silent_Strider »

dvdcollector wrote: Sat Oct 23, 2021 1:53 pm I just want to remove some languages from a multi language mkv or/and change the default language, etc. Can this be done?
Sure, just not with Handbrake. Use MKVToolnix instead.
dvdcollector
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Re: "Video Pass thru" ?

Post by dvdcollector »

Thanks, I assumed "auto passthrough" just means "leave it the heck alone, whatever there is" and it seemed logical for something like that to be available always - after all, what can be difficult about just copying 1:1.

Thanks for the hint about MKVtoolnix, I'll look into it, although already dislike it being a tool for one format.

"Not with HB; HB is a video transcoder."
- apparently not solely - it does seem to handle audio in some capacity. ... Even though people usually imply an audio channel also being in the container when talking about "a video" :)
Inserting a processing module that just forwards data would be trivial and practical IMO. And if you really want to nitpick - mathematically doing something 1:1 could probably still be part of a generic concept of transcoding, just that source and destination sets happen to be identical / an optimized implementation does absolutely nothing but forwarding.
The program structure for it will certainly be there, if it's implemented in a sane way, I dare say.
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s55
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Re: "Video Pass thru" ?

Post by s55 »

Thanks, I assumed "auto passthrough" just means "leave it the heck alone,
Not Quite. It means, passthru, when supported, encode when not. The latter part is the gotcha

You can set this up on the audio behaviours screens and you can see on there what passthru options are supported.

Inserting a processing module that just forwards data would be trivial and practical IMO.
Actually, not so. HandBrakes engine is built for transcoding, not passing through video. There are many complex gotcha's to passthru.
mduell
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Re: "Video Pass thru" ?

Post by mduell »

dvdcollector wrote: Sat Oct 23, 2021 4:14 pmInserting a processing module that just forwards data would be trivial and practical IMO. And if you really want to nitpick - mathematically doing something 1:1 could probably still be part of a generic concept of transcoding, just that source and destination sets happen to be identical / an optimized implementation does absolutely nothing but forwarding.
The program structure for it will certainly be there, if it's implemented in a sane way, I dare say.
You should familiarize yourself in detail with the HB architecture and source code before making such assertions.

If you want ffmpeg, use ffmpeg.
dvdcollector
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Re: "Video Pass thru" ?

Post by dvdcollector »

Ok guys, so my hipshot guess about a probable rough architecture for this was wrong, got me there ;)
Thanks for explaining.
I've only done audio stuff before, not video.
Just out of curiosity, could you describe a bit the nature of complex gotchas w.r.t. pass-thru? Not asking for lengthy explanations to steal your time, just some concept name dropping and relations between things, and I might look those things up & familiarize myself a bit.
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JohnAStebbins
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Re: "Video Pass thru" ?

Post by JohnAStebbins »

The "hard" problem with video passthru is maintaining A/V sync in scenarios where the streams are damaged (this frequently happens with broadcast captures) or sources that have non-seamless branches (DVD and BD). To maintain sync, HandBrake needs to sometimes drop frames. This is easy with decoded video frames and both decoded and encoded audio frames. But encoded video frames are inter-dependent with other frames in a sequence. If you drop one, you corrupt an entire sequence of frames.

Output that is out of sync generates a ton of noise on these forums and in our github issues. We've had our share of bugs that resulted in sync issues. We don't want a "feature" that also results in this kind of noise.
dvdcollector
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Re: "Video Pass thru" ?

Post by dvdcollector »

Oh, I see! Very interesting, thanks again for the explanation.
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