LAV Filters - DirectShow Media Splitter and Decoders

[JarrettH]

Originally Posted by lvqcl

Do you use MadVR? It doesn't support deinterlacing in D3D11 mode.

I do! Yes, that must be it!

[littleD]

Hello, I am testing new laptop and decoding capablities. My Apu is ryzen 8645HS

I am quite satisfied with the results, however among my test video samples I found one that is not playable in hardware acceleration. This is 60FPS VP9 video 8K. I presume the problem is in resolution 8 192 x 4 608 that goes a bit over standard. I have no HEVC sample with same resolution to test.

Typical 8k, Vp9, 60 fps file is decoded at 75% usage of codec engine.

Would it be possible to around this maybe in lavfilters or registry in windows? I see headroom for bit higher res decode.

[clsid]

Give link to sample file.

[littleD]

This is just youtube video of nature. It was in webm format but remuxed and cut to matroska. I have investigated some hifi cameras are using this resolution, probably YT in previous times passed resolution as is with no check.

https://limewire.com/d/zMMyg#HdcrHsAwzi

[huhn]

works on RDNA 4 so maybe...

[nevcairiel]

There is no hardcoded resolution check, so if a file doesn't work, the driver probably rejected it.

[RealSnoopyDog]

I have one question related to "IAMStreamSelect" and subtitle streams: how can I identify the subtitle "stream" that disables subtitles? For LAV splitter, IAMStreamSelect::Info returns the name "No subtitles" and the LCID with the value 0xFFFFFFFF . Would it be sufficient to query for LCID == 0xFFFFFFFF for this?

[nevcairiel]

There isn't really any totally positive identification markers, since the interface is limited. But its always going to be the last subtitle stream, it'll always have that LCID value, and always have the same name.

[RealSnoopyDog]

Thank you, this helps

[mark0077]

May I ask all of the resident experts here for a small piece of advice. When downmixing content to stereo, in the past I have used values of 0.71 for center and surround mix, as well as 1.58 for the lfe mix (based on some maths from previous posts which I definitely don't understand ). But when asking a few of the ais like chatgpt/gemini, they are all adamant that if the stereo system is bass managed, that the correct figure for the lfe is 0.316, but for a stereo system with no bass management only, use 1.58.

I couldn't find mention of this on any posts nor could the AI so I can't back it up with any humans. For my system (KEF LS50 Wireless II which takes the 2 channel input and sends the bass to a SVS PB16 Ultra, the AI is as mentioned adamant that because the KEF in this case has its own bass management, using 1.58 would be classed as boosting the bass by 14db. Does any humans care to give their inputs on this one

LFE at 0.316 → –10 dB (reference)
LFE at 1.58 → +4 dB (boosted)
Difference: ~14 dB more bass with 1.58 compared to 0.316

[Sunspark]

AIs hallucinate, and they only know what they are trained on. They won't say "I don't know". They will give you a number.

I use center 1.00, surround 0.71, lfe 1.58.

This is being sent to an old 2.1 system, but as 2.0, the system itself does the crossover to the subwoofer.

I only use 1.58 because I have the sub. If I didn't, it'd be at 0. Center at 1 is OK because ac-3 5.1 downmix to stereo is too quiet. It won't clip. Plus I still need to use compression on top of that.

The mixer is not a gain control as I understand it.

If your system like mine is doing crossover splitting in the system then by leaving out the LFE by setting it to 0 there is nothing for it to cross-over in those frequencies. According to the specs, my system's crossover frequency for the subwoofer is <=150 Hz and >=4 kHz for the satellites (to tweeter afaik).

I am not an audio expert but I believe this is fine based on my reading.

[tebasuna51]

Each user can downmix at your taste, but remember Dolby do not recommend use the LFE channel at all to downmix 5.1 to 2.0.

Remember LowFrequencyEffects is not a channel for all low frequencies, only for some Efects, all channels can have low frequencies and send them to subwoofer if audio equipment have it.

[Sunspark]

I was looking at the ITU recommendations which does talk about LFE, but doesn't provide a recommendation on it just that DVD video will have LFE at -10 and if you keep it, it should be +10.

I started asking AI where is this 1.58 value from? It said it's +4 dB that assumes stereo summing for the rest of what would normally be 10 dB, and that it's a psychoacoustic compromise based on real-world listening. Supposedly you get basically the same value whether you do math in linear space or RMS power so it seemed to work out.

Going further, apparently Dolby does have a lfemixlev so that's interesting too.

Digging further I found something https://datatracker.ietf.org/doc/htm...ection-5.1.1.5 where they provide coefficient values for downmix to stereo including the LFE (as well as variations without it) so that's interesting but I don't think it can be safely used here because my assumption is that LAV uses a hardcode of 1.0 for FL and FR.

                                                                   /FL \
   / \   /                                                       \ |FC |
   |L|   | 0.529067 0.374107 0.000000 0.458186 0.264534 0.374107 | |FR |
   |R| = | 0.000000 0.374107 0.529067 0.264534 0.458186 0.374107 | |RL |
   \ /   \                                                       / |RR |
                                                                   \LFE/

Have I managed to confuse myself further? Yes. ffmpeg does allow for the use of many custom formulas, but we can't use that here.. just those 3 sliders which are constrained to one interpretation.

The above values are probably good, but the downside I think is that everything will be quiet, and you'd have to turn up the volume on the speakers and then back down again because system sounds/games, etc. would be too loud otherwise.. and my speakers don't have a dial or a number indicator to show what volume they're at..

[tebasuna51]

Originally Posted by Sunspark

The above values are probably good, but the downside I think is that everything will be quiet,...

In the doc you link say also:

Matrices for 3 and 4 channels are normalized so each coefficient row sums to 1 to avoid clipping. For 5 or more channels, they are normalized to 2 as a compromise between clipping and dynamic range reduction.

The above values must be the half to avoid clipping, for that each user can do other compromise, for me it is not use LFE and limit the surround coeficients.

[Sunspark]

I understand the Windows mixer doesn't use the same values, apparently they are licensed and they didn't want to pay the fee to Dolby, so they came up with their own values. It's not bad, just different.

Maybe one day a Front slider will appear and then it will be possible to try all the different formulas people have come up with.

Update: Currently experimenting with 1.0 C, 0.5 S, 0 LFE. Seems to be pretty decent for dialogue clarity.

[nevcairiel]

Just assume front is 1.0 and then re-calculate the other values based on that, all you do is change the overall volume when you also change front, which shouldn't be required.

Although the matrix listed above can't be input anyway, because it also cross-mixes the rear channels (Rear Left into Front Right, etc), which isn't currently an option. If you want more fancy mixing, I would recommend to use an actual audio mixer.

[tebasuna51]

Originally Posted by Sunspark

...Seems to be pretty decent for dialogue clarity.

Just for that, some automatic downmix let the dialog volume to low.

[Siso]

With LAVFilters-0.80.0-13 I can't preview x265 in subtitle workshop 6.3.4. LAVFilters-0.80.0-12 works fine.

[nevcairiel]

Originally Posted by Siso

With LAVFilters-0.80.0-13 I can't preview x265 in subtitle workshop 6.3.4. LAVFilters-0.80.0-12 works fine.

This should hopefully be resolved in the latest already.

[Siso]

Originally Posted by nevcairiel

This should hopefully be resolved in the latest already.

It is working now, thank you.