faq.txt

rockbox掌上游戏机源码,包括pc仿真和小机代码

     doesn't. If the piece of (expensive) electronic doesn't have a power
     source and your mic doesn't either, it does not work!  A PC sound card or
     md player usually has a power output (same pin where the sound goes
     through, dc value) for feeding the FET of an electret condenser capsule
     (see above) (and this power could also used to feed a mic amplifier), but
     the Archos hasn't (it's a line in and no mic in!).

     If you want to know more on microphone powering, read this:
     http://www.hut.fi/Misc/Electronics/circuits/microphone_powering.html.
     (As described, you also need amplification.)

Q66: I can't start rockbox when the charger is connected. What am I doing
     wrong?
A66: If your device is off and you connect the charger, the Archos charger code
     is started immediately. You can then start Rockbox with holding down the
     ON key for several seconds. Hold the key down a really long time, until
     you see the Rockbox logo!

Q67: Why can't you implement a cross-fader? That would be so cool!
A67: Please read our NODO faq. http://www.rockbox.org/twiki/bin/view/Main/NoDo#3_Crossfade_between_tracks_

Q68: My screen is all black/white when I run Rockbox on my Recorder!
A68: This bug has been fixed in the later versions of Rockbox. Upgrade!

Q69: Where are the FM controls for the FM Recorder?
A69: In the menu: FM Radio

Q70: I installed/renamed ajbrec.ajz (or archos.mod) but I am still booting
     with another version of firmware.
A70: When looking on the hard disk the Archos firmware only matches the first
     ten characters of the file name.  Because of this files like 
     ajbrec.ajz.bak or ajbrec.ajz-20030404 match and are loaded.  To 
     prevent this from happening, give the it a file name that differs in 
     the first 10 characters, e.g., ajbrec.bak.ajz. 

Q71: Help! My recorder crashes when I copy files to it!
A71: Yes, the recorder can crash when you copy several gigabytes of
     files to it. The explanation is simple: Copying several gigabytes
     of files through USB requires a long period of sustained disk
     activity and drains more power than the batteries of the recorder
     can store. A long copy will eventually drain the batteries to the
     point where the recorder can no longer function and it halts.
     This even happens when connected to the charger, since the power
     drain is more than the charger can provide! If the recorder halts
     while connecter to the charger, the batteries will recover and
     after a short while it will reboot the Archos firmware in charger
     mode. To make it worse, depending on the USB drivers of your
     system it can cause your system to crash as well, or confuse it
     to the point it needs a reboot.

     There is no solution, just some tips:

     - Connect to the charger when copying lots of files. This will
     not prevent the problem, but it will take longer to happen.

     - Make sure you have "Deep Discharge" disabled.

     - Switch off the "Backlight On When Plugged" option.

     - Use USB 2.0. Transfers will be much faster.

     - Copy incrementally. With fully charged standard batteries it
     should be capable of sustained copying for 2 - 2.5 hours.

Q72: What should I know about digital I/O connector on my jukebox?
A72: The Recorder models have a connector for digital audio output using the
     common S/PDIF standard (Sony/Phillips Digital Interface). This jack is
     not present on the Studio/Player/FM Recorder models. By using the digital
     output in combination with high class external equipment, you can get
     much better sound quality out of your jukebox. This is because you can
     use better DA-converters and better amplifiers, plus you eliminate the
     analog audio connections between the jukebox and your equipment that can
     introduce noise and distortion.

     The Recorder and the FM Recorder models are able to record from digital
     sources, too. The digital inputs don't have the 15kHz lowpass filter like
     the analog inputs and you are sure to minimize the noise floor.

     Although S/PDIF can be an electrical or an optical signal and there are
     many devices that support both, the socket on the jukebox is for
     electrical signals only! Some devices have sockets that look the same,
     and can take either an optical or an electrical cable, but sadly this is
     not true with the Jukebox.

     If you want to connect your amp with digital input (RCA type) to the
     output of your Recorder you need an adapter cable (3.5mm stereo jack to
     dual RCA jack). Plug the 3.5mm stero jack into the digital I/O socket of
     your jukebox and the red RCA jack (right channel) into the digital input
     socket of your amp and that's it. You don't have to enable the digital
     output, since it's always on. The sound settings on the digital output
     are always flat, your volume, bass, treble, bass boost, loudness settings
     won't have any effect here, that's why fade in/out won't work,
     either. The sampling frequency of the digital output is the same as the
     sampling frequency of the mp3. It's therefore possible that your external
     equipment won't be able to synchronize to the output of your jukebox if
     you have mp3's with sampling frequencies other than 32, 44.1 or 48kHz
     (The pitch shift function also modifies the sampling frequency!).

     For recording digital signals on the Recorder, use the white RCA jack
     (left channel) and plug it into the digital output of your CD player, MD
     player or whatever. Don't forget to select digital input in the recording
     settings!

     Note that some adapter cables exist with different color coding, so if it
     doesn't work try to swap red and white. The tip of the 3.5mm jack is the
     digital input, the ring is the ouput. For recording digital signals on
     the FM Recorder, you need a special 4-pole 3.5mm plug (shaft = ground,
     tip = left channel analog line in, first ring (next to tip) = right
     channel analog line in, second ring = digital in).

     If you want to connect devices with optical inputs/outputs, you need a
     small converter box which converts your signal from electrical to optical
     (for digital output from the Archos) or optical to electrical (for
     digital recording in to the Archos).

Q73: How do I unsubscribe from the rockbox mailing list?
A73: The same way you subscribed, but you send an 'unsubscribe' request to the
     mailing list server instead of the 'subscribe' one you sent before.

     This is all mentioned on the same web page: http://www.rockbox.org/mail/

     Please please please pretty please with sugar on top, DO NOT attempt to
     mail unsubscribe requests to the mailing list itself. That will only
     annoy more than 400 readers and will have no effect on your subscription.

     In fact, you NEVER unsubscribe to ANY mailing lists by mailing unsubscribe
     to the list's address. You might as well take the opportunity to learn
     this right away.

     When you first subscribed to the mailing list, you were sent a welcome
     mail from the server. It contained information about the mailing list and
     instructions on how to unsubscribe. It is considered a good habit to keep
     such welcome messages from mailing lists.

     In addition to all this, every mail that is sent out to the rockbox
     mailing list has a set of standard headers that offer info about the
     mailing list: how to post, how to unsubscribe, where to find the mailing
     list archives etc. Sensible mail clients can display these headers.

Q74: What is the Recorder V2?
A74: The Recorder V2 is essentially an FM Recorder without the radio. It looks
     and works like the FM Recorder except for the radio, and has LiIon
     batteries. It is meant to replace the older Recorder model.
     NOTE! The first V2 Recorders were in fact real FM Recorders with the
     radio parts still mounted. If you are lucky, the FM radio might work in
     your V2, try it!

Q75: Why is there a Radio option in my Rockbox for V2?
A75: Some of the first V2 units had an FM radio in there, so if you're one of
     the few lucky ones, you can use the radio fine.

Q76: What does "dir buffer is full" mean?
A76: It means you have more files in a single directory than you have
     configured Rockbox to support. See Q53.

     Solution: Increase the "max files in dir browser" setting.

     The 2.2 release contained a bug that set the default buffer setting
     to 0, giving the dir buffer full error.

     Solution: Upgrade to 2.3.

Q77: Why are you developing X when you should be doing Y?
A77: You make the common mistake of confusing Rockbox development with that of
     commercial projects. There is not much of an agenda for the development
     of Rockbox. Anyone who wants to write new features can do that.

     If there is a current "huge emphasis" on the X functionality, it is
     because one or more developers, decided he/they wanted to write it. It's
     not because "Rockbox project management" decided function X is a more
     important feature than anything else.

     That is the nature of Free Software: People write code that scratches
     their own itches, or that simply is fun to write. Everybody working with
     Rockbox is doing it for fun. A wide or narrow audience actually has only
     little bearing on the choice of features to implement.

     The moment someone with a bit of time to spare and the necessary
     programming skills (or a will to learn them) feels function Y is a
     sufficiently useful feature, it will be written.

     (That could be you.)

Q78: How do I control the recording frequency and quality?
A78: Linus Nielsen Feltzing replied to a similar question on April 17th 2004,
     and this is a cut'n paste of his reply that can be read on the following
     URL:
     http://www.rockbox.org/mail/archive/rockbox-archive-2004-04/0814.shtml

     SAMPLE RATE

     Controls the amount of samples per second, basically which frequencies
     that can accurately be reproduced during playback. Lower frequencies
     produce smaller files, for two reasons: 1) The amount of data to be
     compressed is smaller and 2) the data is easier to compress, since higher
     frequencies are not present.

     BIT RATE

     Controls how many bits per second that is required for accurate live
     transmission of the compressed audio. When you compress the data harder
     (meaning worse sound quality), the bitrate gets lower.

     STEREO VS MONO

     A mono file doesn't necessarily have to be smaller than a stereo file.
     It all depends on the encoder. The MAS does produce smaller files with
     mono.

     MAS QUALITY

     The MAS uses VBR for compression (yes always), which means that the
     bitrate varies from frame to frame, depending on how compressable the
     data was at that point in time. This allows for a more even quality, and
     also smaller files if the data is easily compressed. The MAS can generate
     frames with bit rates ranging from 32kbit/s to 192kbit/s (MPEG1) or
     8kbit/s to 160kbit/s (MPEG2).

     The MAS quality setting is just a way of selecting an average bit rate
     according to the following table (quality 0 is on the far left):

      FREQUENCY        BITRATE IN KBIT/S
      ------------------------------------------------------
      44100Hz stereo:  75, 80, 90, 100, 120, 140, 160, 170
      22050Hz stereo:  39, 41, 45, 50, 60, 80, 110, 130
      44100Hz mono:    65, 68, 73, 80, 90, 105, 125, 140
      22050Hz mono:    35, 38, 40, 45, 50, 60, 75, 90

     (This table can be found on page 38 in the MAS3587 data sheet.)

     MPEG VERSIONS

     The different MPEG versions use different sample rates:
      44100, 48000, 32000: MPEG version 1
      22050, 24000, 16000: MPEG version 2
      11025, 12000, 8000: MPEG version 2.5 (not an official standard)

Q79: How can I make rockbox play tracks in CD order?
A79: You have two options.

     1: You can rename all tracks to have the track number in front of them
     (01 - track1.mp3, 02 - track2.mp3, ...). Just make sure to zero-prefix
     the number properly so that 10 will play after 09.

     2: Make a playlist for each album and play that instead of the .mp3
     files.

     No, you can't make Rockbox use the track number id3 info for this.

Q80: Why does Rockbox say that I only have 18Gb free space on my 20Gb disk?
A80: Because the disk manufacturers have a different definition of Giga than
     the rest of the computer world does.

     Read more about it here:

     http://personal-computer-tutor.com/abc3/v30/vic30.htm