dave2002.alt
This is an alternative weblog for the existing dave2002 weblog hosted at dave2002.pitas.com. This features material on weblogs, music, art, theatre, travel, news and software and hardware, amongst other things

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Saturday, July 30, 2005  

Compressed audio files and streaming audio


I've been revisiting audio files in the last few weeks, following the BBC's Beethoven Experience during which they made all the symphonies available in MP3 format at 128 kbps encoding. I, like many others, downloaded all of these, but I found them a little infuriating. Some of the performances are very good, but I just found the audio quality a bit tiring. This prompted me to check out compression formats again.

There is evidence that apart from lossless compression methods, that it is often possible for experienced musicians to detect the difference between an original source and a compressed copy. Less trained listeners will often accept lower quality, perhaps because they don't know what to expect. Some classical music can sound satisfactory at rates as low as 96 kbps (MP3, but more complex sounds will need higher data rates. Some music works moderately well at 128 kbps (MP3) but this is not always the case, and higher rates will be needed for good results. Most listeners will find it hard to detect much difference between MP3 compressed audio at 192 kbps or higer and the original source.

There has been discussion about which compression formats are best. This is not by any means certain, with some users preferring WMA, and others preferring Ogg Vorbis or MP3 - there may even be people who prefer Real Audio formats. Many writers have criticised MP3, but their justification for doing so seems uncertain. At high bit rates MP3 should give good results, as should most of the other methods. At lower bit rates MP3 may indeed be less good than some other methods, but all methods will give poorer results at low bit rates. Here I am not too interested in low bit rate compression, as I really don't like the sounds produced by low bit rate compression. It may be necessary sometimes, but should not be used for sounds where audio quality is a major part of the listening experience.

The quality of an MP3 encoding does depend on the encoder used. A few are apparently significantly better, though most do well at higher rates (say 192 kbps or above). THe better ones will also do reasonably well at lower rates, and here there can be significant differences between different encoders. Some of the better ones are those which use the LAME encoders, though these are not the only ones which give good results.

One problem with encoding is that some newer encoders use VBR (Variable Bit Rate) encoding - this may not be compatible with all MP3 players, though may give better results with compatible players.

Most MP3 decoders are very similar, though again there are slight differences. Partly this is because, apparently, the specification for decoding is tighter than for encoding, and there isn't too much to go wrong when implementors develop these. Most good MP3 decoders should sound very similar.

Winamp is an MP3 player which represents a reasonable reference standard, both for features and also for sound quality.

What I didn't realise is that most MP3 players now use at least 24 bit processing internally, and this can result in a 24 bit output which is applied to the DACs. If it's required to generate CDs from and MP3 source, this requires conversion back to 16 bit PCM. Some software simply truncates bits, which can give some slight extra distortion. Although this should not be too significant, better software allows dithering, which can subjectively give a closer approximation to the original 24 bit values. When generating WAV files, or burning audio CDs (not MP3 audio) from MP3s, for preference dithering should be applied to give better results. There are some converter tools which provide this facility.

I did try some tests myself on MP3 encoding, and I found that up to 192 kbps there were sections of a test CD which I could distinguish between low and high bit rate encodings - higher being preferable. Above 192 kbps personally I found it hard to be sure of any significant difference, though for preference I would always prefer the original source.

I also found some streaming audio radio stations, some of which are now putting out high quality audio streams. One is Radio Bartok from Hungary, which has an MP3 stream at 320 kbps. NRK Alltid Klassisk from Norway also puts out a high quality stream.

I am going to revise the posting shortly, to provide some references to justify the claims made here. I will also enhance the list of high bit rate streaming audio stations.

posted by David | 8:29 pm
(3) comments

Wednesday, June 01, 2005  


Sardinia - Nuraghe
Originally uploaded by dave2002.

Sardinia - Nuraghe -using flickr to post blog entries



This is a picture of a nuraghe, one of those curious stone buildings they have in Sardinia. They are actually rather large, and also rather old, dating back over 2000 years. They appear to be some form of community building, perhaps a castle or some other similar form of fortification.

The other feature of this post is that this is not done using the Blogger.com interface, but instead is done from the flickr blogging interface. I'll be over there in a few seconds to check that it all worked.


PS: This appears to have worked OK, except that the heading doesn't look right.
I'll see if I can put this right by editing the text/HTML directly.

PPS: Having just discovered that now one doesn't have to explicitly generate headers for entries posted using blogger, it does still seem necessary to do this for entries posted using flickr. Pity!

posted by David | 8:38 pm
(0) comments

Thursday, May 12, 2005  

Commenting


Since Google took over Blogger there have been a number of improvements, including enabling the use of newsfeeds and providing a commenting system. I've finally noticed the commenting, and turned it on - or at least made new comments visible.

I've had to tinker with the settings a bit - in the end I settled on Show the comments, but to use a pop-up window. This means that comments don't appear automatically on the weblog, but only when the comment link is selected. I did wonder if the Hide comments option would hide the comments but make them accessible by a link - but it doesn't - it completely hides them!

I wonder how many others with older weblogs haven't thought to do this!

I'll get round to putting an iconic link to the newsfeed feature in shortly. In the meantime you can access the newsfeed at dave2002alt.blogspot.com/atom.xml

posted by David | 10:17 am
(1) comments

Tuesday, April 19, 2005  

Furling


I've mentioned using furl several times, both here and elsewhere, but now I'm trying to get the latest furled entries into my weblogs. I know it's not the best place to do it, but here they are:

Actually I tell a lie. I tried to put the code inside this entry, but blogger wouldn't let me put the code here, so I'll have to put it in the template after all - so the following paragraph is already in error.

Later - when I get round to it, as they say, I shall move these somewhere else where they will perhaps be more useful.
If you want to do this with your own weblog, then get over to furl, get yourself an account, and then pick up the code. I don't know if other tools, such as spurl also have this type of feature, but will check this out.

posted by David | 4:16 am
(1) comments

Friday, March 04, 2005  

Wireless tinkering - a RetroSpective


I have now succeeded in getting my old Powerbook 1400c computer to operate wirelessly. I have achieved this by buying Dell TrueMobile wireless cards from ebay and using the 7.2 drivers from Orinoco. There have been a few glitches, but it does seem that these are now operating OK. Actually I also bought a "new" 1400 machine in order to keep the original machine working - for example having a spare machine for spares. The additional one is a 1400c 133 MHz so the processor is only 80% of the speed - though the actual speed also depends on the memory in the machine.

This post is actually being made from one of the 1400 machines - the original one, but both are currently working wirelessly. The machines are very slow when working on the Internet - and this seems almost unavoidable nowadays. They work faster with additional memory, and at the current time one has been upgraded to 56Mbytes, the other is still at 40 Mbytes. Both have to use MacOS 8.6 or MacOS 9.0 in order for the wireless drivers to work. I tried the earlier Orinoco drivers in an attempt to make the original machine work with MacOS 8.0, but that failed. Rather than install the later OS versions, I installed a complete system on a 512Mbyte x40 Compact Flash card, and the machine now boots up from that. It's really good that the machine is now very quiet, as the disk is hardly used at all.

Using these old machines is a bit retro, but does demonstrate feasibility. They are perfectly capable of functioning as simple web servers, and experiments have shown that the performance limitations for simple web pages are more likely to be due to the slowness of ADSL upload than the server. On the local LAN a 500 mbyte file loads in about 1 second, but over ADSL it takes 20 seconds at least.

posted by David | 5:16 am
(0) comments

Monday, January 24, 2005  

Systems tweaking



I've been trying to tweak a computer system which was particularly sluggish after installing Blinkx. The machine only has 128 Mbytes of memory, so that's an obvious problem. In the end I decided to abandon Blinkx and replace it with the new Yahoo Search - but even here I decided to prevent it from loading up at startup or login time. I used the great little tool WinPatrol (Scotty dog) to get rid of any unnecessary startup programs. Remember - you don't really save that much time by having all those programs you hardly ever use sticking around in your System Tray, but you do lose a lot of time at startup when everything is loading. You can also check how well your processor is doing using the Windows Task Manager, and if you select the right options from the View menu you can get a lot of information - which tasks are using up CPU cycles, which are generating page faults and which are taking up a lot of memory. I'm now being ruthless - anything which isn't really necessary is not allowed to start. This makes things run ever so much quicker. Spyware and other software may try to reclaim their place in your System Tray - and also memory, but if you use WinPatrol regularly you should be able to prevent this happening. I will probably upgrade the memory on the machine to make it less problematic, but nevertheless I suggest that preventing all but the most important programs from running will make a very big difference. You can also tweak the priorities of the programs if you want to get more oomph, though this can cause some extra problems, and you may not be able to regain control of the machine easily. There are utilities available for handling the priorities of running tasks in a more effective way than Windows does, but unless you are desperate to try them it probably makes sense to do the major prunining suggested here first.

posted by David | 10:42 pm
(0) comments

Thursday, December 30, 2004  

Setting up wireless

I have by now built up experience of configuring wireless networks, and configuring end user laptops for use with wireless LAN (Wi-Fi) systems. There are some horrendous pitfalls, and I have found that some users report that it is easy, while others have great difficulty. Problems can arise even for very experienced users who do installations almost every day. I believe that most problems will affect Windows users, though Apple Mac users will not always be immune from problems.

The most basic installation is one which allows an end user to connect to the internet. Using a wireless router, often an ADSL modem/router device this should be the simplest form of connection. Possible areas of difficulty are:

  • Failing to configure a network card correctly
  • Entering the network name incorrectly
  • Entering an encryption key incorrectly
  • Trying to access a network with too weak a signal
  • Trying to access a network which requires MAC address authentication
Frustrating as most of these are, they are generally easy to fix, but the problem for the end user is that he/she does not usually know this.

There are some other big problems - some mentioned below - see big dial up user problem and connecting desk top machines in weak/no signal areas.

Most users will probably find it easier to use the software which comes with their network card, rather than to use anything provided within Windows. This particularly applies to users who have not yet installed the SP2 updates for Win XP, but even XP users with the SP2 update may have difficulty. My first piece of advice is to try the software which comes with your device first - it'll probably make things simpler. I'm sorry - I've almost forgotten users who use older systems, such as Win NT, Win 98 or even Win 95. Things are just really tough for you guys. If you can, update to Win NT as soon as possible. The Pro version is definitely better, even if it does give Microsoft more revenue.

If you do this step correctly you should be able to pick up the network you are trying to connect to. Some network operators hide the SSID (identification name) of their network, which makes this harder. If you are in control of the network, then it may be useful to turn on the SSID visibility while adding a new computer to the network, as this will allow you to check that the network is visible.

It is obviously important to make sure that the network you are connecting to is the right one, and that the name is entered correctly. Often you don't actually have to enter the name if you can connect to the network, but if the SSID is hidden then you will have to enter the name explicitly.

For private networks operators may use an encryption key. Although WEP keys are known to provide only weak security, it is better than nothing, so it is important to use the correct key if WEP encryption is used. Personally I would recommend the very tedious process of using a long key (128) and typing the whole thing in using hexadecimal notation. This usually requires typing in a 26 character identifier which contains the letters and digits A-F, 0-9, Any randomly generated sequence of 26 characters of this form will do - you don't have to worry about what they "mean" - they're just numbers as far as the network is concerned. Thus

abac 1249 97f1 02d5 853a dafe 89


will be a possible sequence - run them all together to form

abac124997f102d5853adafe89

Some cards provide a password feature which can generate these long keys, but my view is that these are unreliable. If you can make it work for you then fine, but the chances are that you'll save time by doing things the hard way and typing in the long string. It's very easy to make a mistake, so group the characters in (say) blocks of four as above, and type very carefully. Some setups require an additional character, such as a preceding dollar ($) sign to indicate that the key is in hexadecimal.

Make sure that you write your password down and keep it secure. Avoid keeping this information on your computer if possible, though you may be able to recover it later from the router if you are the system adminstrator.

Most networks which are working will provide a good signal over a reasonable area, but it is possible to have weak signals in some locations. If possible try to connect first when close to the base station. It is surprising how often users do not know where the base station is, and often in public places the so-called "hot spot" is not really that close to the transmitter. There may be reasons for this which don't need spelling out here. If you can find out where the base station is, then it is a good idea to move close to it to check the connections. Obviously this is only realistic with portable equipment, such as PDAs and laptops, so if you are trying to connect a desk top PC you will probably have to try to connect in the intended usage location. You may be lucky, and it may work OK, but if not then try to borrow a laptop or PDA to check that. If the signal is really weak there will be no way that you can connect directly, so no amount of reconfiguring will get round that. I'll come back to this later.

The most likely situation is that you will configure the network card to run correctly, and that the signal will be adequate.

Some network operators also block access to computers which are not designated as belonging to their network. This is a useful precaution for home users. However it is easy to forget this, and this can make it difficult when adding a new user device. If you are the operator then turn off this feature while adding the new device in, and then turn it back on once the router has captured the MAC address of the new device. Alternatively, if you are really worried about security issues, find out the MAC address of the network card, and type it in explicitly to the router. This is unlikely to be a problem with public networks, as the operators will want to be able to provide services to users with unknown devices. They will use other methods to ensure that their networks are protected from rogue users, though they will probably not provide much in the way of protection for the end users against other users.

OK - so most of you will have got this far without problems, but some will still not be able to use the network you have set up. I'll explain about this in the next section.

Big dial up user problem
You may have set up your card correctly, set the SSID and WEP key, and ensured that you have access to the network, and be close enough to the base station. Your network card software is indicating a good signal, so you open up a web browser and hope to see a web page. Instead you see that you get a page unavailable message. The first thing to try is restarting your machine, or closing it down and then starting it up again. This may fix the problem, as sometimes full reconfiguration only takes place after restart. However there is a problem with Windows which many users do not know about, and which will still prevent many users from accessing the new network.

It is possible that even after doing this your browser will not pick up the wireless network, and your browser will appear to be offline. If you try to force the browser online, then you will see a dial-up connection window. This will not contain the name of your wireless network, but rather a list of other dial-up connections.

Alternatively you may try to set up a connection via the Start menu. There may be an option to see your available connections, and you may find that there are several dial-up connections, plus your new wireless network available. Selecting the wireless network will probably still not work!

Solution and possible explanation
What is the solution to the problem outlined above? One which seems to work reliably appears to be drastic, but should do the trick. First, for each dial up network you have already set up on your machine, open it up, and write down all the important details. This will probably include:

  • ISP name
  • telephone number
  • user name
  • password
The telephone number and user name should be available in the dialogue box, and you should know the password, or have it written down somewhere. If you've lost your password (because you've been relying on Windows to remember it for you) then it might be good idea to use your dial-up connection to contact your ISP and get them to send it to you, or to get them to reconfigure your password before going on to the next step. If the only form of connection you have which works is dial-up, do that before anything else.

You do not actually have to make a connection to each ISP in order to extract the information you need to store - just open up the connection dialogue and write down the details, then Cancel the connection.

Once you have captured the information needed for each dial-up connection you are ready for the drastic step.

Open up the Control Panel - you can find this from the Start menu. It is probably easier in the older Classic view. Then open up the Network Connections control panel, and you should see your wireless connection - hopefully working apparently (!!), and you will also see your older dial-up connections. For each of the dial-up connections use a right click to select, and then Delete - YES - Delete it. Do this until you have no more dial-up connections left. Most probably there'll only be one connection left at this stage - the wireless network. When you use your browser next it'll only have one place to go, so it'll use that. You may have to restart the machine in order to do that.

If I'm right, and I hope I will be in most cases, you should soon be able to get your wireless network working.

Using the wireless network

Once you have got the wireless network working and are able to browse web pages most of the work has been done. For most users this is all they need. You may want to test the coverage, for example if you are using a laptop to check out the coverage for a connection to a desktop machine which was mentioned earlier. Checking out coverage is most easily done by connecting to a streaming video or audio service, such as a BBC radio or TV news channel, and then walking away from the base station. If you can walk all the way to the proposed site of your desktop installation without losing the streaming service then coverage should be sufficient. If you can't then that will at least confirm that there is a connectivity problem due to coverage, and you may be able to use other methods to fix that - see below.

With luck you will now be able to do most of what you want with the wireless network. However, you may still need to fix your dial-up connections - since you may have by now deleted them all in order to get wireless connectivity working.

Reinstating the dial-ups
You may need to reinstate the dial-up connections which you have perhaps deleted in order to get wireless working.

To do this go to Control Panel -> Network Connections, and for each dial-up account create a new connection. Use the information which you saved when you deleted each dial-up connection earlier. You will probably go through the panels with answers as follows:
  • Network Connection Type: Connect to the Internet
  • Getting Ready: Set up my connection manually
  • Internet Connection: Connect using a dial-up modem
  • Connection Name: Type the name of your ISP in the following box
  • Phone Number to Dial: Type the phone number below
  • Internet Account Information
As you create each new dial-up connection on the last panel in this sequence you may notice a box which suggests that you should "Use this account name and password when anyone connects to the Internet from this computer." You should untick/uncheck this box, as if you leave it you will probably not be able to use the wireless network again - the connection problems will return. You should also see a box "Make this the default Internet connection." Decide whether this really is going to be your default connection, and tick/check appropriately. If in doubt it is probably best to untick/uncheck this, as the defaults can be set up later.

The reason the problems arise is because when the original ISP dial-up accounts were set up, the most sensible thing was for all the connections to go through that account. A few years down the line, and this is no longer the case. There may be other ways of fixing this problem, but this is one which I've found that works.

Good luck with that!

I have one more thing to deal with, for those who may be trying to connect a desk top machine.

Connecting desk top machines in weak/no signal areas
I've indicated that there may be some problems with desk tops in weak signal areas. If you are running your own network there are several solutions. One is to move the base station to provide better coverage. With an ADSL modem/router this will normally be close to a telephone point, and you may also want this to be linked to a another PC which is used for controlling/administering the modem/router. You may not be able to move the base station far and still satisfy these constraints. You can try using a different modem/router, but this is an expensive solution, and will very probably not fix the problem. You can extend the ethernet cable to your modem/router to allow it to be resited, but you won't want to extend it far because that introduces a cabling problem which perhaps you were hoping to avoid.

If you don't mind running the whole of your network wirelessly, and you have several telephone points, then you can move the modem/router device to a telephone point which is closer to the target area. This may now require a new wireless connection to be set up to a machine which was previously connected using cables. This is probably not a very good solution, as it weakens security, and downgrades the connection speed for any machines which are connected via cables. It is however feasible to do this, and some modem/routers can be managed quite effectively this way. Moving the modem/router to an upstairs location may improve coverage considerably. Although this solution is not very good - it may be good enough for many users.

The solution I came up with when I had this problem was to use an external wireless adapter linked by a USB cable to the target desk top machine. I noted that the signal strength was adequate outside the room I wanted to connect to, but useless inside it. Putting the wireless adapter unit outside the room with a long USB cable has provided a reliable solution. I was warned that using long USB cables might cause a problem, but in my case I can say that it has been very satisfactory.

I almost forgot the Apple Mac/iMac/iBook/Powerbook users I mentioned earlier ....

Apple users

Many modern Apple machines come wireless ready. For laptops there may be a slight tendency to lose connections in public areas. Sometimes they re-connect automatically, but this doesn't always happen. Generally one of several brute force approaches may work:

  • Turn off the Airport, then turn it back on
  • As above, but open a new Internet Connect Window, and reconnect to the chosen network
  • As above, but try to connect to a different network first, then reconnect to the desired network
  • Make sure that the WEP key is correct if needed (but it's usually not for public networks)
  • If you are using a laptop in a public area, move around to find a better signal
  • Reboot your machine
  • Try again later! (the network may be down, or overloaded ...)
I haven't found a consistent way of doing this, but I know that the problems I've experienced also affect other users of similar machines. It can be frustrating sitting next to someone (e.g a PC user) who's got a system working, and being unable to connect to the same network that they're on, but it happens. It can also happen that several people will not be able to connect to a network - for example in a hotel lobby. It may take a long while before they talk to each other to see if it's a network problem!

I hope that these notes will help some of you with wireless connections and you won't all have to suffer the pain which I have been through during the last couple of years. I also hope that things will continue to get better as technology and management of infrastructure improve.







posted by David | 7:29 am
(0) comments  

Things seemed to have changed round here

Things seemed to have changed round here since I last posted to this blog. The interface appears to be much easier to use - though whether this is really the case only time will tell. It looks as thought the title facility now works - before I think it only worked for premium users. Nope - this was misleading. The preview feature makes it look as though it works, but the postings don't show this. Thrify users, like me, will have to work out their own ways of getting title headings to appear.
This only requires a very little knowledge of HTML though, but to really do titles properly may require more effort to build up indexes etc. Just putting a header on each posting is relatively trivial.


posted by David | 7:21 am
(1) comments
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