I want to put a QR code on my books which will connect the buyer's smartphone to my website whereon will reside an audio file of the said book. It would consist of about 800 words and last about six minutes. How large would the file be and would it be practicable to download it to the phone, or would the user need to connect to the website every time?
Eric, I think the literal answer to your question is one of those annoying "it depends" on various issues.
In this case, it depends on at least two issues that involve judgements:
1. The format you choose for the audio files, which is a trade-off between file size and audio quality (bigger really is better in this case)
2. How large a file you feel the user could tolerate (thinking about storage, download times, download costs if they're on the mobile network etc).
You can experiment with 1. by recording a sample and then exporting it in various formats (e.g. MP3 with varying compression settings). Audacity is a good candidate for doing this.
However, you could also consider how many times they are likely to listen to the file. If the answer is once (or even twice or three times, perhaps) then there's little point in downloading it. Streaming from the website is essentially equivalent to downloading: the benefit to the user of downloading comes in repeated listens.
Thanks Tony; they are bilingual books for children so,ideally, they would listen to it every time until they'd got the pronunciation right. I could cut it down to three minutes by having each page read only once. I intend to have it recorded in a proper studio so the initial quality is good but the I suppose compress it with different formats so not much quality is lost. The essential question then will be what size of downloaded file could the phone comfortably hold?
Once again it depends on the device and the user. Apple got blasted when it gave away (a present, for no money) a new U2 album and it downloaded onto people's phones. I felt that was a tad ungrateful.
I guess that few people would object to one MB but you might look at limiting the number of files downloaded in total (will they be easily deletable?). Perhaps ask some typical users (or their parents) how much memory is free on their phones.
As a random example, I have a 2min 30s track here downloaded from iTunes that uses 5.7MB, about 2.3MB per minute. It's AAC at 256kb/s and in stereo, you could easily cope with 128kb/s, or even 96kb/s or less, for speech in AAC so you might reckon on one minute in a MB. You need to experiment, as I said before.
Eric Jervis 