******************************************** Frequently Asked Questions by several users, using FalcAMP. updated: 20/04/2000 ******************************************** Q: The MP3 sound plays OK but there are some additional very weird sound effects - like in an old 8-bit SpaceWar-like game. It's the same regardless of operating system and graphics output/resolution. It does it on some Stereo and Joint-Stereo MP3 files. A: You probably heard at what we called the "bubble bug" (because it sounds like a kind of electronic bubbles into the sound !). This was a bug into our layer 3 scalefactors decoding. Now, you should never have this bug anymore: we shot it ! :-) ------------------- Q: ...Perhaps it's a side-effect of the transformation from 44100 Hz to the Falcon replay freq? A: No. It is true that the order 0 interpolation we use for all Falcons without external clock decreases slightly the sound quality (particularly in high frequencies). So, you will not have real CD quality. But it will never adds big noises into the sound ! ------------------- Q: Unfortunately FAMP is not fast enough on my falcon with Afterburner (040 processor running at 32Mhz) to play MP3-files under TOS as well as under N.AES 2.0. What can I do? I don't want to overclock my DSP chip so would an external clock help? A: As surprising as it could be, your Afterburner board cannot really helps FalcAMP, because it speed up only the 68xxx processor, not the DSP56001. FalcAMP needs the power of both processors, so if only one of the two runs faster, this will not resolve all your problems: - If the 68xxx is faster, file parsing and Huffman's decoding will be done easily. The result for you is that using FalcAMP under a multitasking environmnent will be not a problem, whatever you do. So, you will improve your COMFORT using FalcAMP, not the sound quality. - If the DSP is faster, final layer 3 resolving will be easier so that you can choose the maximum sound quality options... but on the 68030 side, you could have serious slow down of your system, especially under a multitasking environment. So, you will improve the SOUND QUALITY, not your comfort ! Yes, an external clock will help a lot your poor 32Mhz DSP ;-) because it will have only 44100 samples to play per second without any interpolation computations, instead of 49170 samples/sec with an interpolation. It will decrease the DSP load about 6%, wich is very important because the DSP is often just beyond 100% of its abilities. With external clock, it is often just below 100 % ! ------------------- Q: I have a speeder in my Falcon called "PowerUp2". This accelerater clocks the CPU with 32MHz, when the CPU doesn't access to the bus. But when running falcamp there is no speed improvement with the accelerator switched on :(. Isn't the CPU calculating, when the Shifter accesses to the RAM? Isn't then some CPU-time wasted? A: If your CPU is overclocked, you must have speed improvement. Until v.0.82á, FalcAMP was designed for monotasking, so you cannot feel improvement. Now, as FalcAMP is interrupt based, under a multitasking environment you can see that there is a big difference between basic and powered Falcons ! ------------------- Q: When *.mp3 is in Directories on a CD Joliet format or more than 8+3 characters format, FalcAMP wrote "PATH NOT FOUND". A: FalcAMP is not responsible for this problem. It is a bad configuration of your desktop. FalcAMP support longnames even those with spaces inside the name. For examle, if you use Jinnee 2.01 and you want to install FalcAMP as an application you have to remove default commandline (%$p) and just set it to open/show *.mp3 files. When you install it as an application under TOS, ask for the full path of the parameter, not just the filename...This way, FalcAMP will always find the files you want to play. After some checks, it seems only Magxdesk caused a real bug by sending strange commandline (not using "ARGS=" in the environment string for sending a file name with spaces). It used a kind of drag'n'drop form but not the standard one. A workaround is now included for this... ------------------- Q: I want your sourcecode ! When will it be available ? A: As soon as Joint-Stereo will be finished, and that requantisation will be coded in a more DSP friendly way. We strongly hope to let FalcAMP works on basic Falcons before releasing them ! Anyway, we already gave parts of our DSP code to the author of DelfMPEG (AMIGA's MPEG player for Delfina DSP 56002 boards). And we are proud to see that our work helped people to make another layer 3 player. This is a great reward for our work. ------------------- Q: Some people said that your player have a low sound quality, is that true ? A: It is true that we cannot get the same accuracy than PCs or Macs which use double precision numbers. The DSP use 24 bits fixed-point numbers. It was not possible to use 48 bits fixed-point numbers because of the required optimization of the player. 24 bit numbers could be not wide enough to store some results without negligible error. Most of the time this error is really weak compared to AMP's C result (lower than 0.01%). It could seldom range between 0.1-0.5% of error. So it is really hard to notice any difference (we compared WinAMP and FalcAMP in realtime, and we were not able to say which played best). Also, many people used old releases of FalcAMP which have a really low computing accuracy. Furthermore, many people have not an external clock on their Falcon and so, the music must be interpolated by FalcAMP. And the used order 0 interpolation give relatively poor result compared to a "clocked Falcon". Also, people forgot that Join-Stereo is not yet supported. So, for Joint-stereo files, the sound of FalcAMP cannot be compared with other players yet. ------------------- Q: When will we have joint-stereo support ? A: Soon ! In fact, the Joint-Stereo support is ready for some files but it is too slow to run on a basic Falcon (and there are bugs). Splash wants to listen to joint-stereo on his basic Falcon, and so, decided to make completely new requantization subroutines, based on optimized ISO sourcecode. Wait and see...