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  1. #1

    LMS AAC/M4A gapless

    Setup:
    • LMS 7.9.0-163 running on Synology 213air connected to Wi-Fi router via LAN cable
    • 1 x Squeezebox Touch, 2 x Squeezebox Radios, 1 x Squeezebox Receiver - all connecting over Wi-Fi
    • LMS library either ALAC Apple Lossles (scanned in on iTunes) or AAC/M4A 256kbps downloads from iTunes

    Been listening to my digitised + iTunes music colleciton as one library via LMS for many years around the house. Much of my collection is scanned in from CDs, but for the last three years I've mostly been downloading from iTunes to save physical space in the house. I downloaded David Bowie's live album 'Stage (2017 Remaster)' as 256kbps AAC from iTunes recently and noticed split second audible gaps between the tracks when there is crowd noise. This really surprised me, as I know LMS is gapless and I have many, many mix, live and continuously-segued CDs that play perfectly gapless in their ALAC Apple Lossless digitised versions. The album plays gaplessly on my iPod Nano, so it's not a problem with the album's actual audio.

    Now I stop to think about it, I guess most of my downloaded iTunes collection has silence between album tracks, so buying this particular live album could be the first time I've really noticed that an album from iTunes doesn't play perfectly gapless on my Squeezeboxes via LMS. Guessing it's not a pre-buffering issue, as ALAC files are much larger than 256kbps AAC, and transition gaplessly with no problems.

    Anyone experienced this with iTunes downloads or other M4A/AAC tracks on LMS? Anyone know of any LMS or Squeezebox settings that might prevent it? Any other tips?

    Thanks

    Andy

  2. #2
    Senior Member Mnyb's Avatar
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    Experiment for you .

    Disable native AAC in file types and see if the server does a better job decoding AAC than the Today h itself ?

    Hopefully your NAS is a recent model that have the grunt to run faad and SoX.
    ( otherwise test with a computer based lms ).

    Over the years some shortcomings of the built in alac and aac decoder in Touch has been discussed.
    I’m not sure if this gap issue is one of them .
    --------------------------------------------------------------------
    Main hifi: Touch + CIA PS +MeridianG68J MeridianHD621 MeridianG98DH 2 x MeridianDSP5200 MeridianDSP5200HC 2 xMeridianDSP3100 +Rel Stadium 3 sub.
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    Kitchen: Touch + powered Fostex PM0.4
    Misc use: Radio (with battery)
    iPad1 with iPengHD & SqueezePad
    (spares Touch, SB3, reciever ,controller )
    server HP proliant micro server N36L with ClearOS Linux

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  3. #3
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    Quote Originally Posted by Mnyb View Post
    Over the years some shortcomings of the built in alac and aac decoder in Touch has been discussed.
    I’m not sure if this gap issue is one of them .
    Gapless AAC has been discussed a numebr of times - one of the issues is the file format - IIRC unlike MP3,AAC in a M4A format has a file structure which if not set up right then the boundaries between files is apparent. I think the trick is to force LMS to always do AAC to Flac decoding - that can removes the "boundary" between files and make gapless appear. Older players always transcoed but newer player have native AAC which means the boundary issues is apparent.

    OP should read other posts such as
    http://forums.slimdevices.com/showth...-fully-gapless

    which links to the thread where andyg says AAC gapless is not there in newer player (2012).
    http://forums.slimdevices.com/showth...rking-properly

  4. #4
    Thanks for the replies. Just tested the changes both threads mentioned (turning off sync between players and turning off native AAC transcoding) and neither worked. With both changes, CDs scanned in as ALAC play perfectly gaplessly, but AAC doesn't.

    I mostly listen to shuffled playlists on my Squeezeboxes, so it's possible I've never noticed the AAC gapless glitches before, but I think it highly unlikely - I have almost 4,000 tracks downloaded from iTunes, so many of these must have gapless sections - Paul Daper's recent 'Spooky Action' being one, which I know I've played in full several times (my keen ear would've noticed the glitches in between tracks that I'm now hearing). But I'm not aware of changing anything in my LMS or NAS.

    Anyone else got this problem with gapless AAC files on LMS? Is this something I can report as a bug to be looked into and hopefully resovled for the next version avaialble on Synology? I'm on version LMS 7.9.0-163 .

    Any other potential solutions?

    Thanks again.

    Andy

  5. #5
    Just a thought... I disabled (what I thought were) unused plugins a few months ago. Is it possible I've disabled one (3rd party or otherwise) that may have prevented this bug)?

  6. #6
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    Quote Originally Posted by AndyTwizzle View Post
    Just a thought... I disabled (what I thought were) unused plugins a few months ago. Is it possible I've disabled one (3rd party or otherwise) that may have prevented this bug)?
    Plugins generally enable playback. So if playback happens (albeit with gaps) and plugin is disabled - the plugin is unlikelyt to be related.,

    Did you read the thread I referenced ?

    Basically disable "natiev" playback for AAC and M4A in WebUI Setting/Advanced/Fuiletypes (don't forget to click apply) and see if there is a difference.

    If you play or sync with the Squeezebox receiver transcode will happen automatcially.
    so for example
    * If you played AAC through Receiver - it could be gapless.
    * If you played AAC through synced Touch and Receiver - it could be gapless.
    * if you played AAC synced through both Touch and Radio - there would be gaps.

  7. #7
    Hi yeah, I disabled all native AAC/M4A in the settings, but gapless AAC albums still have a momentary gap between tracks. Any other ideas?

    Andy

  8. #8
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    Accordinging to https://www.synology.com/en-global/k...es_my_NAS_have

    The processor on your LMS server seems to be a Marvell Kirkwood 88F6282 which a single core prcoessor with no hardware Floating point support (i.e. no FPU) . Transcoding does a lot of floating point artihmetic which can load a processor with no FPU especially a single core. It is possible the processor is underpowered to do transcoding without delay (i.e. a gap) and without trasncoding AAC will have a gap.

    You could test by installing LMS on a PC .

  9. #9
    Senior Member pinkdot's Avatar
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    I don't know if AAC is gapless in every setup or not, but what DSM version is installed on your nas?
    Why don't you update LMS to 7.9.1 166?
    -LMS on Raspian Stretch -> 2x Radio
    -RPI 3 (Archphile), Aune S6 - Exposure 3010S2 - PMC FB1i

  10. #10
    Quote Originally Posted by pinkdot View Post
    I don't know if AAC is gapless in every setup or not, but what DSM version is installed on your nas?
    Why don't you update LMS to 7.9.1 166?
    I'm on DSM 6.1.5-15254-1, released on 27 Feb 2018. I haven't updated to the latest LMS as I only upgrade when there's a new packaged-up Beta version available from Synology's Package Center (plus I don't know how to manually install it myself).

    Thanks

    Andy

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