4.0.1pre is now available

So, here's 4.0.1pre, and here's what's in it:

- The revised G5 JavaScript nanojit. Which is, you know, faster. And therefore doesn't suck. (G5 only)

- The AltiVec accelerated WebM video decoder (VP8, to be more precise). (7400/7450/G5)

- The scroll-slower-upper-thinger to make Flash applets not quite artifact as badly. They will still smear with scrolling, but less noticeably. (All)

- All the Firefox 4.0.1 fixes to date. There are quite a few; some don't affect us, but there are some security-related issues in here (none public) and some crash fixes. (All)

Plus this bonus hotness I snuck in:

- Tuned movie playback for all platforms, which affects not just WebM but also Theora. This causes slower Macs to buffer more decoded frames and smooth out the audio even if the video is choppy. The settings are different for G5 than G4/G3 because G5 has much bigger bandwidth due to its wider front-side bus. (All)

- Enabled AltiVec compositing also for libpixman. This means that pixel compositing is now done with AltiVec operations, which affects just about everything in the browser, really. The effect is subtle, but smooths out animations nicely and improves repainting speed. (7400/7450/G5)

Before you download this, consider grabbing a video and watching it in 4.0s just to see your starting point. I recommend going to www.youtube.com/html5 and signing up for the WebM trial (you don't need to have an account for that, just join with the link at the bottom), then viewing this video about Google's fiber experiment. If that video comes up in Flash, you did it wrong. This is a good test video because it has scenes with high data rates (the product manager on camera) alternating with lower ones (the animation sequences in the middle, and the title card and end card), so it's a good general overview.

On my G4/450 Sawtooth (7400) -- and by the way, I still don't support systems slower than 1.25GHz for video -- this video is pretty much unplayable with 4.0s. The audio is immensely fractured and you can forget about any video frames.

On my iBook G4/1.33 (7450) with 4.0s, the video and audio are extremely choppy with Energy Saver set to Automatic. Some frames appear and the audio is at least intelligible, but still fractured. It improves marginally at Highest.

On my quad G5 in Reduced with 4.0s, it plays in fits and starts. The snippets it does play are normal, but its data pipeline poops out and it has to buffer again repeatedly between them. On my quad G5 in Highest, it plays with only rare audio artifacts. I don't have a G3 handy right now (my PDQ is in pieces on my workbench waiting for a new hard disk).

So, now install 4.0.1pre and play it again. On the Sawtooth G4, the audio is artifacted, but now intelligible. The video is a glorified slideshow, but frames do appear at least occasionally. Hey, WebM video is pretty hefty to decode, and this computer is eleven years old, so whaddya want? :P

On my iBook G4 in Automatic with 4.0.1pre, it skips frames frequently, but the audio is nearly intact. In Highest, it still skips, but fewer, so I'd consider this playable.

On my quad G5 in Reduced with 4.0.1pre, it now plays perfectly.

Please note that Mozilla's streaming code is not terrifically robust. For example, if you enlarge or contract the Google video gadget using the arrows icon, then you start getting video artifacts when something overlays the video, and the buffering starts to seize up. The code doesn't seem to be able to handle a sudden drop in throughput well (a similar effect occurs when you change processor speed midstream in System Preferences). You can fix this by rewinding back to the beginning of the video, and then the streamer will be able to properly buffer. It looks like Mozilla's code just doesn't know what to do with the CPU changing performance characteristics abruptly or the video being dynamically resized as the video plays, but in fairness this is probably a lot to ask of it.

By the way, only my quad G5 in Highest could handle enlarged video fully (in Reduced, it got choppy), and don't even think about playing it full screen, because we can't hardware blit (this poor G5 got absolutely crushed trying to play Big Buck Bunny at 1920x1080 in software). This will only get better and still has some getting better to do, but it's a start, and the combination of buffer adjustments and VP8 VMX decoding does help.

Note that the WebM container decoding is still in C, and the actual portion of Mozilla's code that does the conversion to pixels (before they are blitted, which is VMX-accelerated) is also "just" in C. Firefox 5 is adding SIMD-based decoding of JPEG images; in at least older versions of libogg there was some AltiVec support; and I'd like to at some point have an entire AltiVec-accelerated content chain, all the way from raw data to rendering. There is some code that I think may be trivially converted to AltiVec (either in C or assembly) to gain us even more speed on the non-optimized sections, but that's for a later time.

Here is what I need from you wonderful beta hounds:

- G3 owners: Expect scrolling to be slower when a Flash applet is on-screen, but is it too slow? WebM video probably won't play hardly at all on your system, but it should not crash (which would mean AltiVec code snuck in). Is there any playback degradation with Ogg and VP3/Theora video using the new buffer settings?

- G4 owners: Improvement noticible? Above 1.25GHz, is video at least acceptable, even if it's a bit choppy or imperfect visually?

- G5 owners: Improvement noticible? How is JavaScript performance now?

Mozilla is planning an April 26th release for 4.0.1, and so will we. Anyway, go get:

• G3
• G4/7400
• G4/7450
• G5

You should get an upgrade notification when 4.0.1 final is available, so grab it and have at it, and post your observations in the comments.