Recording on ipod (was: nano recording volume)

[bot47]

Hi!

I just started recording using my iPod nano and current rockbox cvs using the headphone jacket, but it's REALLY quiet (but works) even though I used a quite powerful input. Is there any trick to make it record more usefully? Increasing the volume and the record gain does not help that much!

[petur]

see commit 18 Dec 01:52 by Barry Wardell:

FS#6096. Recording on PortalPlayer targets (H10, iPod Video, iPod 4g, iPod Color, iPod Nano). * Fix failed compile of enc_config.c when HAVE_MPEG2_SAMPR is not defined. * Fix bug in AIFF encoder header creation on little endian targets. * Add recording screen keymaps for H10 and iPod. * Move pcm_playback PP specific code to target tree. * Add recording code to wmcodec drivers. * Add pcm_record code. Some problems still remain: * Playback doesn't work after recording until Rockbox is restarted. * Gain control not implemented. * Only 16-bit/44KHz for now. The hardware should be capable of up to 24-bit/96KHz. * Line-in recording not tested on H10

[linuxstb]

All evidence so far suggests recording doesn't work on the Nano.  It was enabled in CVS by mistake, and we decided to leave it just to try and confirm for sure that it doesn't work.

Are you sure it's working at all?  Do your recordings contain recognisable audio?

(I would be very happy to be proved wrong).

[bot47]

Yes, they do. Do you want me to upload some?

[barrywardell]

It looks like the mic through headphones socket has to be specifically enabled on  4g/color iPods through a GPIO port. I wonder if the same thing is the case for the nano? See pcm_init_recording() in firmware/target/arm/pcm-pp.c for an idea of what I mean.

[linuxstb]

Yes, they do. Do you want me to upload some?

No, but I'm curious to know what kind of input you used.  i.e. was it a mic, or something at line-in level?

[Febs]

I recorded last night with my 5G iPod video, using a line-input dock made by Soap.  

Using a Sony ECM-907, the recorded signal is present, but barely audible above the noise floor.  As  a point of reference, what I was recording is a show that I play seven times a week.  I had previously recorded the show with an iriver H120, using the same microphone, same mic placement, etc.  In that recording, AGC safety mode limited the overall gain to about 28dB.  

I also tried using my Total BitHead headphone amp to boost the signal.  That gave me a little more signal, but also more noise.

I haven't yet had a chance to try recording from a line-level source.

Recording was unstable generally.  Rockbox would almost invariably eventually freeze during the recording.  I wasn't able to detect any pattern about what caused the freezes.

[linuxstb]

Just a warning - don't judge the quality of recording on the ipods by the code in Rockbox at the moment.  It's only really "proof-of-concept' code, and no effort has yet been made to setup the ADC optimally.

[Febs]

I understand completely.

[podshot]

well recording with a nano works. tried it with line out from my computer and it shows some activity... but its barely hearable in playback..  sorry for my english but i am still a bit drunk...  yeah i know this is just a "proof of consept"  but i tought i would just verify that recording on a nano works!;D i hope someone would work on improving it. ( i would do it if i had any coding expiriense)

well keep up the good work!
rock box rules!

[Llorean]

Have you actually got a recording that is recognizable as the source material clearly enough to be definite, or are you judging that it works just from peakmeter movement?

[mlind]

...its barely hearable in playback.. 

[Llorean]

Yes, but "barely hearable" could mean "I can barely hear a faint staticy noise" or it can mean "I can barely hear anything at all" or it can mean "I can barely, but significantly, identify the audio I was trying to record" and I would like a clear clarification of this.

I would also like to know if he used the dock adapter or the headphone jack.

[podshot]

i used the headphone jack.
 "I can barely, but significantly, identify the audio I was trying to record"!
well i recorded a song and i was able to listen to it in playback but in realy bad quality and it was realy quiet. but it is recognisable!

[bot47]

Sorry for me not answering immediatley
I tried two things. Both worked (at least kind of):
1st) A quite loud output from my soundcard to the headphone jack.
2nd) The Line-In Pin of the Dockconnector works, too. I attached my (!!broken!!) iPod Radio Remote and I got a static noise which sounded like the 87.5 Mhz background noise and 87.5 Mhz is the default channel it gets tuned into when attaching it the first time to the iPod original OS.