A chance to talk to FlatpanelsHD's reviewers.
By Kuschelmonschter
Very good review! Thanks for that.

If I understand correctly, YouTube HDR works via Chromecast Ultra with HDR10 capable displays. I actually thought that HDR10 was only specified for HEVC and that VP9.2 uses different metadata formats. At least this is how I interpreted the table in this news article.

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By Rasmus Larsen

Well, VP9 encoded video streams can use both HLG and ST.2048 EOTFs, the latter being what is generally referred to as PQ (Perceptual Quantizer). A VP9-PQ stream passes "HDR_TYPE_HDR10" onto the display device, so for example a TV can process it as a HDR10 stream.

I'm not 100% sure how the metadata differ between the two but here's Google's full documentation:
By Fjodor2000
If using Chromecast as a mediaplayer, streaming video to it e.g. from a PC, will that video be compressed or re-encoded when transferred to the Chromecast/TV?

I.e. is there any risk of a video quality loss, compared to using a standard mediaplayer connected directly to the TV via HDMI?
By Kuschelmonschter
You should have read the article more carefully ;) ...
If you know Chromecast all this is trivial but if you are new to the product you should know that Chromecast in fact takes over the video stream to the video streaming server. This ensures that you get the best possible video quality that the streaming service can deliver, and that you can use your mobile device for other tasks in the meantime. This is very different from technologies such as Miracast that actually mirrors the entire screen. Chromecast can also do that from an Android device or PC/Mac but it is not its main purpose as a product.
The mobile device or PC only initiates playback. Chromecast just gets a link to the stream on the server. So playback does not go via the mobile device or PC. No transcoding is done. Chromecast choses the best quality stream based on the network connection speed.
By Fjodor2000
Thanks for the clarification!

But in that case, I suppose you're limited to only watching content with video formats that the Chromecast can decode? If so, how good is the codec support on Chromecast? I suppose it only supports those formats listed in the review, i.e. HEVC, VP9 Profile2 and MPEG4 (H.264)?

So just a device for watching TV streaming services over the Internet. Not really a suitable replacement for a media player...
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By Rasmus Larsen
Yes either that or use a local video server that can transcode on-the-fly. Of course that reduces video quality somewhat. Besides the one mentioned it should also decode MPEG2. But remember that these are base video formats. Things like .mkv .mp4 and .avi are containers, and things like H.264 / AVC are profiles under MPEG4. So it has quite good support.

Still, I don't see Chromecast Ultra as an alternative to a media player for local media. It's still first and foremost a streaming device.
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By Boban
Can someone please tell me if a video recorded on an iPhone 12 pro max in Dolby Vision can be displayed via Google Chromecast Ultra on an LG B6 and actually display the file in Dolby Vision? It works on LG GX if you plug in a hard drive with the file. Anyone?