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Transcoding Fast Forward
01-05-2014, 11:59 (This post was last modified: 01-05-2014 14:19 by Mr Frog.)
Post: #1
Transcoding Fast Forward
Hi

I've been using MinimServer as UpnP installed on QNAP TS-212 NAS (ARM x19 processor) to stream music to Naim ND5XS network player and all works great streaming FLAC. Everything is hard wired via ethernet and the NAS is next to he player - rather than long cable runs or wireless.

I've just changed System settings on MinimServer (via MinimWatch) to transcode - flac:Wac24 for better sound quality (Naim players seem to prefer WAV to FLAC) and still working great.

However, I have noticed that the fast forward function on the Naim n-Stream control app (which I use on iPad to select tracks etc) now seems to be rather jumpy and have a delay when scrolling through a track - almost as if it needs to catch up. Sometimes it simply restarts the entire track rather than forwarding to the selected area (e.g. 1 min 35 secs) of the track.

Incidentally, it works perfectly if I change the System settings on MinimServer and leave the data to stream the original FLAC files - and no longer transcode flac to wav.

Is this due to transcoding and is there a fix being developed to allow smooth fast forward/rewind of tracks to locate certain parts of the music - as I experience without transcoding?
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01-05-2014, 15:10
Post: #2
RE: Transcoding Fast Forward
(01-05-2014 11:59)Mr Frog Wrote:  Hi

I've been using MinimServer as UpnP installed on QNAP TS-212 NAS (ARM x19 processor) to stream music to Naim ND5XS network player and all works great streaming FLAC. Everything is hard wired via ethernet and the NAS is next to he player - rather than long cable runs or wireless.

I've just changed System settings on MinimServer (via MinimWatch) to transcode - flac:Wac24 for better sound quality (Naim players seem to prefer WAV to FLAC) and still working great.

However, I have noticed that the fast forward function on the Naim n-Stream control app (which I use on iPad to select tracks etc) now seems to be rather jumpy and have a delay when scrolling through a track - almost as if it needs to catch up. Sometimes it simply restarts the entire track rather than forwarding to the selected area (e.g. 1 min 35 secs) of the track.

Incidentally, it works perfectly if I change the System settings on MinimServer and leave the data to stream the original FLAC files - and no longer transcode flac to wav.

Is this due to transcoding and is there a fix being developed to allow smooth fast forward/rewind of tracks to locate certain parts of the music - as I experience without transcoding?

Please see this thread for information about why this is happening.

How did you create the FLAC files? Are they compressed FLAC or uncompressed FLAC? Do you know whether they contain a seek table?
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01-05-2014, 16:20 (This post was last modified: 01-05-2014 16:48 by Mr Frog.)
Post: #3
RE: Transcoding Fast Forward
Hi Simon

Thank you for the quick response - much appreciated

I used dbpoweramp to rip the CD's using uncompressed FLAC. Other files are also uncompressed downloads.

There are no seek table options within dbpoweramp, but when the uncompressed files are streamed as FLAC, the fast forward or seek function (n-Stream) works faultlessly. It's only when I transcode (flac:wav24) to serve transcoded to Wav files to the player that I can no longer use this seek function.

As such, the uncompressed FLAC files can use the seek function without any problem whatsoever but not if transcoded to wav - so I'm not sure if a seek table in the FLAC files or compressing them will alter anything - because it works fine for FLAC.

Is there a way to get the transcode issue fixed?
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01-05-2014, 16:37 (This post was last modified: 01-05-2014 16:39 by simoncn.)
Post: #4
RE: Transcoding Fast Forward
(01-05-2014 16:20)Mr Frog Wrote:  Hi Simon

Thank you for the quick response - much appreciated

I used dbpoweramp to rip the CD's using uncompressed FLAC. Other files are also uncompressed downloads.

There are no seek table options within dbpoweramp, but when the uncompressed files are streamed as FLAC, the fast forward or seek function (n-Stream) works faultlessly. It's only when I transcode (flac:wav24) to serve transcoded to Wav files to the player that I can no longer use this seek function.

As such, the uncompressed FLAC files can use the seek function without any problem whatsoever but not if transcoded to wav - so I'm not sure if a seek table in the FLAC files or compressing them will alter anything - because it works fine for FLAC.

Is there a way to get the transcode issue fixed?

The slow seek time when transcoding is caused by using uncompressed FLAC and also not having a seek table.

Without transcoding, seeking is done by jumping to a given byte offset in the FLAC file. The time taken to do this is very small and doesn't vary much with not having a seek table or using uncompressed FLAC.

With transcoding, the byte offset in the WAV stream needs to be translated to a byte offset in the FLAC file by reading through the FLAC file. The time taken to do this is increased very considerably by not having a seek table or using uncompressed FLAC.

Please refer to the other thread for how you can add a seek table to your files or change the FLAC compression level. Of these two options, the shortest seek time when transcoding will be achieved by adding a seek table.
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01-05-2014, 16:48
Post: #5
RE: Transcoding Fast Forward
Incidentally, as an experiment I've just installed Asset UpnP trial version and can confirm that both uncompressed FLAC files and transcoding to Wav works identically with the seek/fast forward feature on n-Stream. No issues at all, whatever settings or format is used.

As such, it looks like a potential issue with MinimServer and transcoding and not the FLAC files themselves.

Is there a way to get the transcode issue fixed?
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01-05-2014, 19:09
Post: #6
RE: Transcoding Fast Forward
(01-05-2014 16:48)Mr Frog Wrote:  Incidentally, as an experiment I've just installed Asset UpnP trial version and can confirm that both uncompressed FLAC files and transcoding to Wav works identically with the seek/fast forward feature on n-Stream. No issues at all, whatever settings or format is used.

As such, it looks like a potential issue with MinimServer and transcoding and not the FLAC files themselves.

Is there a way to get the transcode issue fixed?

I am doing some experiments with an alternative approach for FLAC transcoding. This would require you to have a stream converter (ffmpeg or avconv) installed. From preliminary tests, it looks like this greatly reduces the seeking delay.
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02-05-2014, 07:57
Post: #7
RE: Transcoding Fast Forward
(01-05-2014 19:09)simoncn Wrote:  
(01-05-2014 16:48)Mr Frog Wrote:  Incidentally, as an experiment I've just installed Asset UpnP trial version and can confirm that both uncompressed FLAC files and transcoding to Wav works identically with the seek/fast forward feature on n-Stream. No issues at all, whatever settings or format is used.

As such, it looks like a potential issue with MinimServer and transcoding and not the FLAC files themselves.

Is there a way to get the transcode issue fixed?

I am doing some experiments with an alternative approach for FLAC transcoding. This would require you to have a stream converter (ffmpeg or avconv) installed. From preliminary tests, it looks like this greatly reduces the seeking delay.

Sounds good and I look forward to its release. Thanks for all your help.
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02-05-2014, 09:54
Post: #8
RE: Transcoding Fast Forward
(02-05-2014 07:57)Mr Frog Wrote:  Sounds good and I look forward to its release. Thanks for all your help.

Unfortunately, further tests on other equipment and with other files have been less encouraging. I will continue to work on this.
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13-05-2014, 23:05
Post: #9
RE: Transcoding Fast Forward
(01-05-2014 19:09)simoncn Wrote:  
(01-05-2014 16:48)Mr Frog Wrote:  Is there a way to get the transcode issue fixed?

I am doing some experiments with an alternative approach for FLAC transcoding. This would require you to have a stream converter (ffmpeg or avconv) installed. From preliminary tests, it looks like this greatly reduces the seeking delay.

I have abandoned the FFmpeg approach because of performance issues with FFmpeg's support for seeking FLAC files. Instead, I have made some changes to the current implementation to significantly improve seek performance when transcoding a FLAC file to WAV.

The greatest improvement is for FLAC files that don't contain a seek table. There should also be a small benefit for FLAC files that do contain a seek table.

These changes are available in MinimStreamer 0.3.18. I'd be interested to hear how well this performs when seeking your transcoded files.
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15-05-2014, 10:55 (This post was last modified: 15-05-2014 10:56 by Mr Frog.)
Post: #10
RE: Transcoding Fast Forward
(13-05-2014 23:05)simoncn Wrote:  
(01-05-2014 19:09)simoncn Wrote:  
(01-05-2014 16:48)Mr Frog Wrote:  Is there a way to get the transcode issue fixed?

I am doing some experiments with an alternative approach for FLAC transcoding. This would require you to have a stream converter (ffmpeg or avconv) installed. From preliminary tests, it looks like this greatly reduces the seeking delay.

I have abandoned the FFmpeg approach because of performance issues with FFmpeg's support for seeking FLAC files. Instead, I have made some changes to the current implementation to significantly improve seek performance when transcoding a FLAC file to WAV.

The greatest improvement is for FLAC files that don't contain a seek table. There should also be a small benefit for FLAC files that do contain a seek table.

These changes are available in MinimStreamer 0.3.18. I'd be interested to hear how well this performs when seeking your transcoded files.

Hi Simon

Just deactivated the trial version of Asset and activated MinimStreamer 0.3.18

Seeking transcoded files now works perfectly :-)

Thank you so much for all your help
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