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  1.    #1  
    I have a 512 sd card and have 68 songs on it with approx. 118mg of space left. I know it all depends on the length of the track and the quality level it was recorded at but are there any other tricks to maximize the # of songs one can get onto a 512 card?

    Thanks
  2. #2  
    I know you recognized this solution already since and that you are looking for 'other' possible solutions, but... I don't think there really are any. That said, you can best save space by down-encoding the bitrate of your library for playback on the Treo.

    I encode at 64 mbps with no noticeable difference. If you are at 128 now, moving to 64 will double your capacity. (You really shouldn't have any music encoded ANY higher than 128 or you are just wasting space--CD quality is approx than 128kbps (a tad better I think). So encoding at bitrates above 128 does nothing to improve the fidelity which is limited by the underlying fidelity of the original CD. (Maybe DVD music is actually recorded at higher bitrates, I don't know)

    With the capacities and usage you provided above, your average song seems to be 5.8MB (assuming you are using all 512-118 for songs)?? Those are either very long songs, or you have many songs encoded above 128. My average songs are about 1.8MB files at 64kbps. If you down-encoded your tracks to 64, you could have nearly 200 songs and still have the 118MB reserved for other stuff like backups, docs, and videos.

    Audiophiles may disagree with my 64kbps recommendation and (maybe) with a truly great headset (bose or similar), the difference could be perceivable, but for passing time and everyday use, that's what I'd recommend. This will give you much more variety for your listening.

    Hope this was helpful.
  3.    #3  
    Thanks, Will consider down coding the music. Might be a little more effort than i hoped but worth a try if the sound quality holds up.

    Gratzi
  4. #4  
    Might also try creating OGG Vorbis files instead of MP3. That's what I use on my Treo. I encode them at 64k and I can't notice the difference in sound between MP3s at 128 and OGG at 64 (I CAN however notice a difference between MP3s at 128 and 64).

    I use CDex to create my compressed audio files. It comes with both MP3 and OGG encoders (anticipating that a followup question would be how to convert into OGG...).
    Treo 680 GSM since July 2007
    Treo 600 GSM from November 2003 through July 2007
    AT&T (formerly Cingular, formerly PacBell PCS) since September 1998
  5. #5  
    Quote Originally Posted by greenawayj
    CD quality is approx than 128kbps (a tad better I think).
    From a technical standpoint, that's not correct. CD-DA is:
    16 bits/sample * 2 channels * 44100 Hz (samples/second) = 1,411,200 bits/second
    1,411,200 bits/second / 1,024 bits/Kilobit = 1378Kbps (remember that computer scientists have decided that data rates should use 'Kilo' to mean 1024, not 1000).

    That's why a 800 MB data CD can be burned with 74 minutes of CD audio:
    16 bits/sample * 2 channels * 44100 samples/second = 1411200 bits/second
    1411200 bits/second * 60 seconds/minute * 74 minutes = 6,265,728,000 bits
    800MB = 800,000,000 Bytes = 6,400,000,000 bits
    6,265,728,000 bits ~= 6,400,000,000 bits
    Figure in overhead for track data, and the math works even better.

    At any rate, as you know, the MP3 compression scheme typically provides good results at 128Kbps. It is a 'lossy' compression scheme, meaning that you'll always lose information whenever you compress it. There's a big difference in which algorithm is used to compress the data, as they all pick slightly different data to discard. I read an article a few years back that put MusicMatch's compression at the top of the list. But saying that "128Kbps is CD-quality" is not really true.

    (Maybe DVD music is actually recorded at higher bitrates, I don't know)
    I believe they are. I think DVD uses 48000Hz audio. I don't know much about the technical side of surround-sound, but one would imagine that having 5 channels would raise the bitrate of the audio stream quite a bit.

    For better quality, you might try encoding your MP3's with at a VBR (variable bit rate). The software should detect when more/less data is needed to make the audio sound good. I believe PTunes supports VBR MP3 files. Most apps let you set high and low data rates, so you can have much more control over the filesize.

    A typical MP3 encoded at 128Kbps takes up slighly less than 1MB/minute:
    128 Kilobits/second * 60 seconds/minute * 1024 bits/Kilobit = 7,680 Kilobits / 8 bits/Byte = 983.4 Kilobytes/minute (.98MB/minute) Keep in mind that greedy hard-drive manufacturers have changed the meaning of Kilo to 1,000, and Mega to 1,000,000.

    If yours are taking up more space than that, there's something weird going on.

    Hope that helps. I was just going to mention the VBR thing, but I got carried away. At least my CSCI degree is useful for something...

    Nareau
  6. #6  
    Nareau--

    Thanks for doing the math. I was lazy and just quoting a statement I've heard from several sources (don't remember where though). I just assumed it was correct since there seems to be so many more mp3s out there at 128 than at an other bit rate. We all know what happens when one A$$-U-MEs. Anyway, having an EE degree myself, and having hand-manipulated various time/frequency transforms on multiple work sets in college, I should have been smart enough to know that an 80 minute CD at wave quality is full of 'data' so therefore 128 MP3 quality isn't as good when you can get hundreds of minutes of 128MP3 on the same CD!!! Math proves out, I think (although I thought CD was 8bit sample rate--just quibling now)

    Anyway, the math is good to know, but I guess what those sources might really meant is that the 'losses' when recording at 128 and focused on frequencies above and below those perceptible to human ears and at discreet intermediate frequencies which are redundant (or nearly so) again based on the limitations of human ears (combined with audio speaker and headset technologies)?

    Don't know the answer, but I still hold that I can't tell the difference using a regular $15 headset between 64 and 128. The OGG suggestion is great though and one I hadn't thought of.

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