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• I Really Like My New EeePC

  29 août 2010, par Multimedia Mike — General

  Fair warning : I’m just going to use this post to blather disconnectedly about a new-ish toy.

  I really like my new EeePC. I was rather enamored with the original EeePC 701 from late 2007, a little box with a tiny 7″ screen that is credited with kicking off the netbook revolution. Since then, Asus has created about a hundred new EeePC models.

  Since I’m spending so much time on a train these days, I finally took the plunge to get a better netbook. I decided to stay loyal to Asus and their Eee lineage and got the highest end EeePC they presently offer (which was still under US$500)– the EeePC 1201PN. The ’12′ in the model number represents a 12″ screen size and the rest of the specs are commensurately as large. Indeed, it sort of blurs the line between netbook and full-blown laptop.

  
  
  

  Incidentally, after I placed the order for the 1201PN nearly 2 months ago, and I mean the very literal next moment, this Engadget headline came across announcing the EeePC 1215N. My new high-end (such as it is) computer purchase was immediately obsoleted ; I thought that only happened in parody. (As of this writing, the 1215N still doesn’t appear to be shipping, though.)

  It’s a sore point among Linux aficionados that Linux was used to help kickstart the netbook trend but that now it’s pretty much impossible to find Linux pre-installed on a netbook. So it is in this case. This 1201PN comes with Windows 7 Home Premium installed. This is a notable differentiator from most netbooks which only have Windows 7 Home Starter, a.k.a., the Windows 7 version so crippled that it doesn’t even allow the user to change the background image.

  I wished to preserve the Windows 7 installation (you never know when it will come in handy) and dual boot Linux. I thought I would have to use the Windows partition tool to divide work some magic. Fortunately, the default installation already carved the 250 GB HD in half ; I was able to reformat the second partition and install Linux. The details are a little blurry, but I’m pretty sure one of those external USB optical drives shown in my last post actually performed successfully for this task. Lucky break.

  
  
  The EeePC 1201PN, EeePC 701, Belco Alpha-400, and even a comparatively gargantuan Sony Vaio full laptop– all of the portable computers in the household
  

  So I got Ubuntu 10.04 Linux installed in short order. This feels like something of a homecoming for me. You see, I used Linux full-time at home from 1999-2006. In 2007, I switched to using Windows XP full-time, mostly because my home use-case switched to playing a lot of old, bad computer games. By the end of 2008, I had transitioned to using the Mac Mini that I had originally purchased earlier that year for running FATE cycles. That Mac served as my main home computer until I purchased the 1201PN 2 months ago.

  Mostly, I have this overriding desire for computers to just work, at least in their basic functions. And that’s why I’m so roundly impressed with the way Linux handles right out of the box. Nearly everything on the 1201PN works in Linux. The video, the audio, the wireless networking, the webcam, it all works out of the box. I had to do the extra installation step to get the binary nVidia drivers installed but even that’s relatively seamless, especially compared to “the way things used to be” (drop to a prompt, run some binary installer from the prompt as root, watch it fail in arcane ways because the thing is only certified to run on one version of one Linux distribution). The 1201PN, with its nVidia Ion2 graphics, is able to drive both its own 1366×768 screen simultaneously with an external monitor running at up on 2560×1600.

  The only weird hiccup in the whole process was that I had a little trouble with the special volume keys on the keyboard (specifically, the volume up/down/mute keys didn’t do anything). But I quickly learned that I had to install some package related to ACPI and they magically started to do the right thing. Now I get to encounter the Linux Flash Player bug where modifying volume via those special keys forces fullscreen mode to exit. Adobe really should fix that.

  Also, trackpad multitouch gestures don’t work right away. Based on my reading, it is possible to set those up in Linux. But it’s largely a preference thing– I don’t care much for multitouch. This creates a disparity when I use Windows 7 on the 1201PN which is configured per default to use multitouch.

  
  
  The same 4 laptops stacked up
  

  So, in short, I’m really happy with this little machine. Traditionally, I have had absolutely no affinity for laptops/notebooks/portable computers at all even if everyone around was always completely enamored with the devices. What changed for me ? Well for starters, as a long-time Linux user, I was used to having to invest in very specific, carefully-researched hardware lest I not be able to use it under the Linux OS. This was always a major problem in the laptop field which typically reign supreme in custom, proprietary hardware components. These days, not so much, and these netbooks seem to contain well-supported hardware. Then there’s the fact that laptops always cost so much more than similarly capable desktop systems and that I had no real reason for taking a computer with me when I left home. So my use case changed, as did the price point for relatively low-power laptops/netbooks.

  Data I/O geek note : The 1201PN is capable of wireless-N networking — as many netbooks seem to have — but only 100 Mbit ethernet. I wondered why it didn’t have gigabit ethernet. Then I remembered that 100 Mbit ethernet provides 11-11.5 Mbytes/sec of transfer speed which, in my empirical experience, is approximately the maximum write speed of a 5400 RPM hard drive– which is what the 1201PN possesses.

• How to play random part of mp4 file with vlc or something else ?

  13 septembre 2011, par pprzemek

  I have random part (99,9% somewhere in the middle) of the mp4 file. Problem is that it's not in any container or anything just a binary piece of the file in random offset and send to me... it will keep growing but it'll take a while and I need to play content right away.

  I can get all necessary metadata information for that file from other source before I even start receiving those binary data, but :

  1. How to do this ? I mean what headers do I need and how to get them ?
     and
  2. How to later tell vlc (or maybe some other player) that this moov atom (or some other data) that it should use for this part of the file and start playing it ?

• H.264 and VP8 for still image coding : WebP ?

  1er octobre 2010, par Dark Shikari — H.264, VP8, google, psychovisual optimizations

  JPEG is a very old lossy image format. By today’s standards, it’s awful compression-wise : practically every video format since the days of MPEG-2 has been able to tie or beat JPEG at its own game. The reasons people haven’t switched to something more modern practically always boil down to a simple one — it’s just not worth the hassle. Even if JPEG can be beaten by a factor of 2, convincing the entire world to change image formats after 20 years is nigh impossible. Furthermore, JPEG is fast, simple, and practically guaranteed to be free of any intellectual property worries. It’s been tried before : JPEG-2000 first, then Microsoft’s JPEG XR, both tried to unseat JPEG. Neither got much of anywhere.

  Now Google is trying to dump yet another image format on us, “WebP”. But really, it’s just a VP8 intra frame. There are some obvious practical problems with this new image format in comparison to JPEG ; it doesn’t even support all of JPEG’s features, let alone many of the much-wanted features JPEG was missing (alpha channel support, lossless support). It only supports 4:2:0 chroma subsampling, while JPEG can handle 4:2:2 and 4:4:4. Google doesn’t seem interested in adding any of these features either.

  But let’s get to the meat and see how these encoders stack up on compressing still images. As I explained in my original analysis, VP8 has the advantage of H.264′s intra prediction, which is one of the primary reasons why H.264 has such an advantage in intra compression. It only has i4x4 and i16x16 modes, not i8x8, so it’s not quite as fancy as H.264′s, but it comes close.

  The test files are all around 155KB ; download them for the exact filesizes. For all three, I did a binary search of quality levels to get the file sizes close. For x264, I encoded with --tune stillimage --preset placebo. For libvpx, I encoded with --best. For JPEG, I encoded with ffmpeg, then applied jpgcrush, a lossless jpeg compressor. I suspect there are better JPEG encoders out there than ffmpeg ; if you have one, feel free to test it and post the results. The source image is the 200th frame of Parkjoy, from derf’s page (fun fact : this video was shot here ! More info on the video here.).

  Files : (x264 [154KB], vp8 [155KB], jpg [156KB])

  Results (decoded to PNG) : (x264, vp8, jpg)

  This seems rather embarrassing for libvpx. Personally I think VP8 looks by far the worst of the bunch, despite JPEG’s blocking. What’s going on here ? VP8 certainly has better entropy coding than JPEG does (by far !). It has better intra prediction (JPEG has just DC prediction). How could VP8 look worse ? Let’s investigate.

  VP8 uses a 4×4 transform, which tends to blur and lose more detail than JPEG’s 8×8 transform. But that alone certainly isn’t enough to create such a dramatic difference. Let’s investigate a hypothesis — that the problem is that libvpx is optimizing for PSNR and ignoring psychovisual considerations when encoding the image… I’ll encode with --tune psnr --preset placebo in x264, turning off all psy optimizations. 

  Files : (x264, optimized for PSNR [154KB]) [Note for the technical people : because adaptive quantization is off, to get the filesize on target I had to use a CQM here.]

  Results (decoded to PNG) : (x264, optimized for PSNR)

  What a blur ! Only somewhat better than VP8, and still worse than JPEG. And that’s using the same encoder and the same level of analysis — the only thing done differently is dropping the psy optimizations. Thus we come back to the conclusion I’ve made over and over on this blog — the encoder matters more than the video format, and good psy optimizations are more important than anything else for compression. libvpx, a much more powerful encoder than ffmpeg’s jpeg encoder, loses because it tries too hard to optimize for PSNR.

  These results raise an obvious question — is Google nuts ? I could understand the push for “WebP” if it was better than JPEG. And sure, technically as a file format it is, and an encoder could be made for it that’s better than JPEG. But note the word “could”. Why announce it now when libvpx is still such an awful encoder ? You’d have to be nuts to try to replace JPEG with this blurry mess as-is. Now, I don’t expect libvpx to be able to compete with x264, the best encoder in the world — but surely it should be able to beat an image format released in 1992 ?

  Earth to Google : make the encoder good first, then promote it as better than the alternatives. The reverse doesn’t work quite as well.

  [155KB]