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View Full Version : Digital out fails for 64k audio, works for 56k



David Hearst
2004-07-14, 09:39
Dean,

So, I think what you're saying is that the Squeezebox doesn't prevent
non-standard streams from being delivered to its digital outputs. It seems
like it's just passing the data to the digital output and leaving it up to
the playback device to determine whether it supports the format. Clearly, my
receiver is adhering to the "22.050k doesn't work over S/PDIF" rule, while
the SuperDAC happily accepts the non-standard signal. Is that your take as
well?

Also, does this mean the Squeezebox uncompresses MP3 but otherwise does not
alter the data, i.e. delivers it to the digital output at whatever sample
rate and bit depth it received?

I'm now wondering (separate post) whether it would be possible to have the
SlimServer recognize when it receives an MP3Pro signal and pass it off to
Audion for transcoding before streaming it as PCM data.

Thanks for the follow up,

David


-----Original Message-----
From: discuss-bounces (AT) lists (DOT) slimdevices.com
[mailto:discuss-bounces (AT) lists (DOT) slimdevices.com]On Behalf Of dean
blackketter
Sent: Wednesday, July 14, 2004 8:22 AM
To: Slim Devices Discussion
Subject: [slim] Digital out fails for 64k audio, works for 56k


Hi David,

I took a look at that station and it appears to use a 22.050k sample
rate, which doesn't work over S/PDIF, according to the spec. Maybe
your SuperDAC is smart enough to be able to play back non-standard
sample rates.


On Jul 13, 2004, at 3:49 PM, David Hearst wrote:

> Dean,
>
> Here's the link for the station:
>
> http://www.live365.com/stations/vongoober?play
>
> Here's the broadcaster's home page as well:
>
> http://www.vongoober.com
>
>
> I do think this has something to do with the fact that the station is
> broadcast as MP3Pro and thus is being handled by the SlimServer and the
> Squeezebox as bandwidth constrained MP3. I just can't figure out why
> the
> stream works when the Squeezebox feeds my SuperDAC and not when it
> feeds my
> Marantz receiver. What type of stream would you expect to be delivered
> at
> the Squeezebox's output when it receives incoming MP3 stream? Would it
> be
> PCM data? Would its sample rate and/or bit depth be determined by the
> characteristics of the incoming MP3 stream? I'm guessing that whatever
> digital format the Squeezebox outputs in response to the incoming
> MP3Pro is
> supported by my SuperDAC but not my receiver. I just don't know if
> that's
> what we'd expect from the Squeezebox.
>
> Thanks for your help,
>
> David
>
>
>
> -----Original Message-----
> From: discuss-bounces (AT) lists (DOT) slimdevices.com
> [mailto:discuss-bounces (AT) lists (DOT) slimdevices.com]On Behalf Of dean
> blackketter
> Sent: Tuesday, July 13, 2004 2:53 PM
> To: Slim Devices Discussion
> Subject: [slim] Digital out fails for 64k audio, works for 56k
>
>
> Can you post the URL for the failing station?
>
> On Jul 9, 2004, at 3:54 PM, David Hearst wrote:
>
>> Sean,
>>
>> Thanks for the suggestion. I've actually done a bit more
>> experimentation and it's pretty clear that the problem is not 32kHz
>> sample rate. Here's the additional info:
>>
>> I own two Squeezeboxes (an early wireless model and a fairly recent
>> wired model). One is attached to the optical digital input on our home
>> theater receiver, the other is connected to an M-Audio Super DAC 2496.
>> After my original E-mail, I discovered that the Squeezebox /SuperDAC
>> combo was working fine with the 64k stream. I then confirmed that
>> either one of my Squeezeboxes work fine with the SuperDAC. They just
>> don't work with my home theater receiver.
>>
>> To the best of my knowledge, the difference between these internet
>> radio stations is as follows:
>>
>> Success: 56k bit , standard Live365 stream
>> Failure: 64k, MP3 Pro-capable Live365 stream
>>
>> That leads me to a question. I'm just wondering whether you'd expect
>> the digital stream coming out of the Squeezebox to be significantly
>> different in these two cases and, if so, different in what way?
>> Obviously, a simple and not-too-expensive solution would be to
>> purchase another SuperDAC to use with our home theater. I'd just like
>> to understand what the problem is before jumping on that bandwagon...
>>
>> Thanks, David
>>
>>
>> On Jul 9, 2004, at 3:03 PM, Sean Adams wrote:
>>
>>>
>>> David,
>>>
>>> Probably the stream is using a 32KHz sample rate, which is not
>>> compatible with s/pdif (not a squeezebox limitation - just not
>>> supported over s/pdif at all).
>>>
>>> The best solution if you have a receiver which auto-senses the s/pdif
>>> signal is to connect both cables. Then the amp will automatically
>>> fall back to the analog inputs if s/pdif is not available.
>>>
>>> Sean
>>>
>>> On Jul 9, 2004, at 11:27 AM, David Hearst wrote:
>>>
>>>> For quite awhile I've been using my Squeezebox and SlimServer to
>>>> deliver Live365 broadcasts to my stereo using the digital (optical)
>>>> output. It has worked fine for the stations I used up until now but
>>>> it turns out that all of them are being streamed at 56k bit quality
>>>> from their respective servers. Today I tried to set up a 64k bit
>>>> stream in a similar fashion and found that I get no output from my
>>>> stereo. However, if I use the analog outs on the Squeezebox they
>>>> work fine. It's just the digital (optical) output that is a problem.
>>>> All the 64k stream doesn't work, not only do 56k streams work, but
>>>> the WAV audio files in my iTunes library work fine as well when
>>>> played through the digital (optical) output.
>>>>
>>>> Has anyone experienced this? Should the Squeezebox be delivering the
>>>> same type of digital signal output regardless of the stream rate
>>>> received by the SlimServer? Are there any settings I can change to
>>>> overcome this problem?
>>>>
>>>> Thanks for the help,
>>>>
>>>> David Hearst
>>>> david (AT) madd-dogg (DOT) com
>>>>
>>>>

dean
2004-07-14, 10:13
Hi David,

On Jul 14, 2004, at 9:39 AM, David Hearst wrote:
> So, I think what you're saying is that the Squeezebox doesn't prevent
> non-standard streams from being delivered to its digital outputs. It
> seems
> like it's just passing the data to the digital output and leaving it
> up to
> the playback device to determine whether it supports the format.
> Clearly, my
> receiver is adhering to the "22.050k doesn't work over S/PDIF" rule,
> while
> the SuperDAC happily accepts the non-standard signal. Is that your
> take as
> well?
Exactly.

> Also, does this mean the Squeezebox uncompresses MP3 but otherwise
> does not
> alter the data, i.e. delivers it to the digital output at whatever
> sample
> rate and bit depth it received?
That's right.

> I'm now wondering (separate post) whether it would be possible to have
> the
> SlimServer recognize when it receives an MP3Pro signal and pass it off
> to
> Audion for transcoding before streaming it as PCM data.
That certainly would be possible, but isn't currently supported.

-dean
>
> -----Original Message-----
> From: discuss-bounces (AT) lists (DOT) slimdevices.com
> [mailto:discuss-bounces (AT) lists (DOT) slimdevices.com]On Behalf Of dean
> blackketter
> Sent: Wednesday, July 14, 2004 8:22 AM
> To: Slim Devices Discussion
> Subject: [slim] Digital out fails for 64k audio, works for 56k
>
>
> Hi David,
>
> I took a look at that station and it appears to use a 22.050k sample
> rate, which doesn't work over S/PDIF, according to the spec. Maybe
> your SuperDAC is smart enough to be able to play back non-standard
> sample rates.
>
>
> On Jul 13, 2004, at 3:49 PM, David Hearst wrote:
>
>> Dean,
>>
>> Here's the link for the station:
>>
>> http://www.live365.com/stations/vongoober?play
>>
>> Here's the broadcaster's home page as well:
>>
>> http://www.vongoober.com
>>
>>
>> I do think this has something to do with the fact that the station is
>> broadcast as MP3Pro and thus is being handled by the SlimServer and
>> the
>> Squeezebox as bandwidth constrained MP3. I just can't figure out why
>> the
>> stream works when the Squeezebox feeds my SuperDAC and not when it
>> feeds my
>> Marantz receiver. What type of stream would you expect to be delivered
>> at
>> the Squeezebox's output when it receives incoming MP3 stream? Would it
>> be
>> PCM data? Would its sample rate and/or bit depth be determined by the
>> characteristics of the incoming MP3 stream? I'm guessing that whatever
>> digital format the Squeezebox outputs in response to the incoming
>> MP3Pro is
>> supported by my SuperDAC but not my receiver. I just don't know if
>> that's
>> what we'd expect from the Squeezebox.
>>
>> Thanks for your help,
>>
>> David
>>
>>
>>
>> -----Original Message-----
>> From: discuss-bounces (AT) lists (DOT) slimdevices.com
>> [mailto:discuss-bounces (AT) lists (DOT) slimdevices.com]On Behalf Of dean
>> blackketter
>> Sent: Tuesday, July 13, 2004 2:53 PM
>> To: Slim Devices Discussion
>> Subject: [slim] Digital out fails for 64k audio, works for 56k
>>
>>
>> Can you post the URL for the failing station?
>>
>> On Jul 9, 2004, at 3:54 PM, David Hearst wrote:
>>
>>> Sean,
>>>
>>> Thanks for the suggestion. I've actually done a bit more
>>> experimentation and it's pretty clear that the problem is not 32kHz
>>> sample rate. Here's the additional info:
>>>
>>> I own two Squeezeboxes (an early wireless model and a fairly recent
>>> wired model). One is attached to the optical digital input on our
>>> home
>>> theater receiver, the other is connected to an M-Audio Super DAC
>>> 2496.
>>> After my original E-mail, I discovered that the Squeezebox /SuperDAC
>>> combo was working fine with the 64k stream. I then confirmed that
>>> either one of my Squeezeboxes work fine with the SuperDAC. They just
>>> don't work with my home theater receiver.
>>>
>>> To the best of my knowledge, the difference between these internet
>>> radio stations is as follows:
>>>
>>> Success: 56k bit , standard Live365 stream
>>> Failure: 64k, MP3 Pro-capable Live365 stream
>>>
>>> That leads me to a question. I'm just wondering whether you'd expect
>>> the digital stream coming out of the Squeezebox to be significantly
>>> different in these two cases and, if so, different in what way?
>>> Obviously, a simple and not-too-expensive solution would be to
>>> purchase another SuperDAC to use with our home theater. I'd just like
>>> to understand what the problem is before jumping on that bandwagon...
>>>
>>> Thanks, David
>>>
>>>
>>> On Jul 9, 2004, at 3:03 PM, Sean Adams wrote:
>>>
>>>>
>>>> David,
>>>>
>>>> Probably the stream is using a 32KHz sample rate, which is not
>>>> compatible with s/pdif (not a squeezebox limitation - just not
>>>> supported over s/pdif at all).
>>>>
>>>> The best solution if you have a receiver which auto-senses the
>>>> s/pdif
>>>> signal is to connect both cables. Then the amp will automatically
>>>> fall back to the analog inputs if s/pdif is not available.
>>>>
>>>> Sean
>>>>
>>>> On Jul 9, 2004, at 11:27 AM, David Hearst wrote:
>>>>
>>>>> For quite awhile I've been using my Squeezebox and SlimServer to
>>>>> deliver Live365 broadcasts to my stereo using the digital (optical)
>>>>> output. It has worked fine for the stations I used up until now but
>>>>> it turns out that all of them are being streamed at 56k bit quality
>>>>> from their respective servers. Today I tried to set up a 64k bit
>>>>> stream in a similar fashion and found that I get no output from my
>>>>> stereo. However, if I use the analog outs on the Squeezebox they
>>>>> work fine. It's just the digital (optical) output that is a
>>>>> problem.
>>>>> All the 64k stream doesn't work, not only do 56k streams work, but
>>>>> the WAV audio files in my iTunes library work fine as well when
>>>>> played through the digital (optical) output.
>>>>>
>>>>> Has anyone experienced this? Should the Squeezebox be delivering
>>>>> the
>>>>> same type of digital signal output regardless of the stream rate
>>>>> received by the SlimServer? Are there any settings I can change to
>>>>> overcome this problem?
>>>>>
>>>>> Thanks for the help,
>>>>>
>>>>> David Hearst
>>>>> david (AT) madd-dogg (DOT) com
>>>>>
>>>>>

Jahf
2004-07-28, 10:07
>> I'm now wondering (separate post) whether it would be possible to have
>> the
>> SlimServer recognize when it receives an MP3Pro signal and pass it off to
>> Audion for transcoding before streaming it as PCM data.
>
> That certainly would be possible, but isn't currently supported.

Consider this a second request for transcoding of non-PCM compatible data :)

I have a couple of News stations that seem to only work from when
connected to analog. I imagine some folks only connect digital and just
assume a silent station is a problem at the source.

It would be great if the SB would take non-standard rates and zap them
through a filter in the same way I convert Oggs on the fly.