Support and General Use > Audio Playback, Database and Playlists
Toggle playback sample rate iriver H100 H300?
saratoga:
The sample rate test does not do what you think it does, but by all means if I'm remembering wrong feel free to figure out how to clock the device at 48k.
Julian67:
--- Quote from: saratoga on July 20, 2013, 12:22:58 PM ---The sample rate test does not do what you think it does, but by all means if I'm remembering wrong feel free to figure out how to clock the device at 48k.
--- End quote ---
I'm a user asking a question on a support forum so it hardly seems reasonable to offer zero information and instead respond by "inviting" me to figure out how to clock the device.
Saying "such and such does not do what you think it does" doesn't resolve any question or issue. One person's "insight" into what another person is supposedly thinking doesn't address anything of the questions posed or points raised.
I'll try again, hoping for an informative response:
The H140 manual states on page 34:
--- Quote ---When saving the optical signal with 48KHz as WAV file,
the Bitrate is 1536Kbps. (48 KHz, 16Bit, Stereo)
--- End quote ---
The H140 manual on page 35 states:
--- Quote ---Optical recording can sample at 44.1KHz or 48KHz.
--- End quote ---
On page 2 (referring to play back):
--- Quote ---The H140 supports WAV types of 11/22/44/48KHz, 16bit, Mono/Stereo.
--- End quote ---
I have just checked with a 22050 Hz sample rate 10000 Hz tone and again this plays back without any sign of sample rate conversion and with the OF's display indicating "22KHz" sample rate and "705K" bit rate.
In the OF the 10000 Hz test tones at sample rates 22050, 44100 and 48000 Hz all play back at identical pitch. In contrast in Rockbox (as with any device using sample rate conversion) each file plays back with clearly different pitch.
The capability to play audio at various sample rates is supported by the codec hardware data sheet, by the specs offered by the device manufacturer, and by the device manufacturer's user manual. In practice the H300 with original firmware does indeed play back 22050 Hz, 44100 Hz and 48000 Hz wav files as claimed in the documentation, which is to say without any sign of sample rate conversion.
It's unclear why playing back the test tones of different sample rates and noting what the device indicates, if the pitch changes, and how this compares to device specification and also other known hardware (with and without sample rate conversion) is held to be an exercise of no value. It seems to demonstrate that either iRiver made the best ever sample rate converter or that the device plays back wav files of supported rates exactly as claimed and indicated. If it doesn't demonstrate this then what is the error in the method?
How is it possible to assert that the device is can't support 48 KHz audio files without sample rate conversion?
saratoga:
--- Quote from: Julian67 on July 20, 2013, 03:09:35 PM ---I'm a user asking a question on a support forum so it hardly seems reasonable to offer zero information and instead respond by "inviting" me to figure out how to clock the device.
--- End quote ---
And I answered you:
'The H100/H300 doesn't support 48k as far as I know, so that option isn't possible.'
If you don't agree, then you get to figure it out yourself or hope that someone else does for you.
--- Quote from: Julian67 on July 20, 2013, 03:09:35 PM ---In the OF the 10000 Hz test tones at sample rates 22050, 44100 and 48000 Hz all play back at identical pitch. In contrast in Rockbox (as with any device using sample rate conversion) each file plays back with clearly different pitch.
--- End quote ---
Well resampling doesn't change the pitch (by definition, resampling is the process of changing sampling rate without changing pitch). So I have no idea what you're doing or what those results mean, but its definitely not what you think it is.
saratoga:
I searched and found this:
--- Quote ---amiconn kugel (Buschel, saratoga - logs): There are several stable targets which don't support 48kHz, e.g. *all* the coldfire targets only support 44.1/22.05/11.025 (and some of them 88.2)
11:44 amiconn Supporting (96/64)/48/32/24/16/12/8 on those targets would require a different base clock xtal - and then they wouldn't support 44.1 & related rates
...
12:22 kugel amiconn: could you possibly switch between the modes?
12:27 amiconn kugel: You can switch between (88.2)/44.1/22.05/11.025.
12:28 amiconn Different xtal for the base clock offering the other sample rates means soldering
...
12:30 amiconn This is a limitation of the audio clock generation in the MCF5249 and MCF5250
...
12:32 amiconn *Iiuc* it could be solved if the dac would be clock master, but since the targets aren't designed that way, this isn't possible either
12:32 amiconn Audio clock master I mean
12:34 amiconn This is why the H1x0 can record non-44.1 S/PDIF natively (and pass it through), but not record analog signals or play back at that rate.
12:35 amiconn In case of s/pdif recording the input is audio clock master
--- End quote ---
http://www.rockbox.org/irc/log-20120929#11:43:05
So it looks like you can do 48k if you're willing to solder a new crystal to the board, but otherwise you have to resample.
Julian67:
Thank you for your very informative reply.
I can demonstrate that low quality sample rate conversion does change pitch. It does so by introducing tones which were not originally present so while the new file does still contain the tone at the original frequency it now also has other tones. Result: the pitch is measurably and audibly different.
Example: source file is 2 channel 16-bit 48KHz file of a 10000 Hz tone.
Convert to 22050 sample rate using low quality (linear interpolator) conversion:
--- Code: ---sndfile-resample -to 22050 -c 4 48_10000.wav linear.wav
--- End code ---
Result:
Listening to the sample rate converted file it has a very obviously lower pitch exactly as suggested by the spectrogram. That is of course a crude example for the purpose of illustration but the difference in sound is practically identical as when toggling between a 44.1KHz and 48KH file on my Rockboxed H140 or H340. One can hear similar tonal differences with most sample rate conversions except the good quality ones at medium and high quality settings.
It doesn't seem likely that iRiver found a way to run a highly demanding good quality SRC on the H340 as the processing power limitation is exactly the same as for Rockbox, so reason suggests they must also be using something like a linear interpolator, as found as default in most PC operating systems and portable audio players. But the original firmware on my H340 can render 22050, 44100 and 48000 Hz files apparently as perfectly as if no rate conversion has taken place, or as though there has been, in real time, extremely high quality conversion that would tax even a processor several times more powerful. If the info from the chat logs above is accurate then how is this possible? Or maybe the H100 and H300 CPUs are not as identical as it appears?
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