A TechLore "Ask the Experts" Question...
Question:
We bought an MP4 player on ebay from Hong Kong, and it says it holds 99 songs. However, after loading 5 songs it says its full. When there are no songs loaded, it says 97 percent of the player is full of recorded files. Can we get these recorded files off and how?
Answer:
Unfortunately, it's unfair of manufacturers to claim that a player holds a certain number of songs. In all reality, the manufacturer can't really say how many songs will fit, because the total capacity of the player is not limited to the number of songs, but by the amount of data storage available. What's worse, there are so many factors and variables that players rated to hold a number of songs may hold much less, and even more than stated. Confused? You're not alone. Fortunately, TechLore is here to help you figure out how many songs your player will hold.
The Number of Songs
As I said above, you can't state how many songs a player will hold. The only known factor is the amount of memory available on the player. Flash memory based players will have less storage capacity than hard disk based players. Currently, flash players have total storage capacities from 32MB to 16GB, while today's hard disk players will tout storage capacities from 8GB to 160GB on the most expensive models.
If the manufacturer of your player is claiming to hold 99 songs, you can expect that the total storage capacity of the player is very low; most likely 64MB, but perhaps even lower. Knowing the total storage capacity of your player is crucial to figuring out how many songs can actually fit.
So did the manufacturer lie to you? No, but they're not exactly being forthcoming with you either. That player can hold 99 songs, but the actual number possible is determined by two other important variables: the length of the song, and the bit rate the music is encoded in. In other words, how big each actual song file is that you want to listen to.
Bit Rates, Song Length, and All That Jazz
Every digital audio file takes up a certain amount of space. How much space is determined by the song's length, and how the song was encoded into a digital audio file.
The most important factor to how many songs your player will hold is not necessarily the codec used to compact the music file in a smaller size, but the bit rate the music is encoded in. The bit rate determines how good the audio will sound compared to the original source. Songs encoded at high the bit rates will sound better than songs encoded at low bit rates, but will result in larger files for each song.
Song length is the other important factor. The longer the song is, the more space the song will take up. I have music tracks that are less than two minutes in length, and other tracks that exceed ten. Music that is five times the length will take up five times the amount of data storage, provided that the bit rate is the same.
Figuring Out How Big a Song Will Be
Using the bit rate and song length, you can actually figure out how much space a song will take up by using a little basic math. You'll need to know the song length in order to figure it out.
Music is encoded in a number of kbps. In normal speak, this means each second of the song will take up that number of kilobits (not kilobytes, which is what makes this complicated). Let's say you have a song that is two minutes long (120 seconds). If you wanted to encode this song at 128kbps fixed rate, the resulting file would be 15,360 kilobits (15.36 Mb). Assuming the player's flash memory is rated in Megabytes (where 1 MB = 1000 KB), then we need to convert the song from Megabits to Megabytes. There are 8 bits to a byte, so the resulting file size is 1.92 MB (note: Windows calculates megabytes on a different scale than memory makers, so Windows will report the file size of your song and total capacity of your player smaller.)
So, if all your songs were two minutes long, and each was recorded at 128kbps, then you would be able to hold about 33 songs on a 64MB player (assuming all 64 MB of space on the player is open for music storage, which is not often the case). At 192kbps, the same 64MB player can hold about 22 songs. Now, if each song were 4 minutes long, the player would hold about 11 songs.
Coming Up With 99 Songs
Manufacturers that tout a specific number will often come up with some kind of average like we've done above, but they typically pick low bit rates and short song lengths in order to tout higher numbers. There's a bunch of ways to hit 99 songs. For example, if each song was assumed to be eighty seconds and encoded at 64kbps, then you'd fit about 99 songs in a 64MB player. Of course, the problem is that most songs are longer than this, and songs recorded at low bit rates usually sound terrible.
If you want to fit more music in your player, there's obviously nothing you can do about the song length, but you do have control how the music is encoded. If you want to carry more music with you, encode using a lower bit rate, or just buy a player with a larger memory. Either way will work.
In your specific case, if your player is indicating that it's 97% full with nothing on it, you may have a formatting issue you need to take care of before using it in the US. Formatting the player will erase everything, but you could render the player inoperable if there is a system file on it that shouldn't be removed. If you decide to try and format it, do so with caution. I'd recommend finding a savvy, experienced friend that can examine the player in person and help you figure out what's going on.
Matt Whitlock - Editor, TechLore.com
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