2017-02-06, 21:49
I apologize for the long post, but I think today I found something out, which might be interesting for other people, who always have been unsatisfied with libreelec's crossfade between tracks and/or gapless audio playback in general:
I use libreelec on pi3 with hdmi audio output and I literally NEVER got accurate crossfading and gapless playback with libreelec until today. There was always an annoying little click and very short gap in the mid of the crossfaded portion. I wrote this twice before and that's been my prime reason, why I signed up to this forum (asking what is meant by paplayer being able to play gapless). There are many people reporting similiar things about gaps with kodi and never get a solution. Seems as if there just exist people who NEVER recognize gaps and clicks playing their audio tracks using kodi/libreelec on the one hand and those who ALWAYS have gaps and clicks (like me) on the other hand. Really odd.
Now for the very first time I got satisfying crossfading, even mixed between flac - mp3 vbr - mp3 cbr etc... And these annoying very short distortions which I had at the beginning of each track (independent to crossfade set or not) disappeared as well. Plus now my gapless concept albums (e.g. "Pink Floyd - The Wall" or "DJ Shadow - Live In Tune And On Time") eventually play gapless!
Here is what I've done:
I generated one ~9 second long 300 Hz sinus wav file. Wav because I wanted PCM as I couldn't believe all the comments in web, claiming lossy formats with variable bitrate causing these problems to be true. Yes, I know this can be part of the gapless issue, but some of my other almost 8 years old devices can play at least flac and constant bitrate mp3 gapless, while kodi for me didn't. I duplicated this wav file 9 times, put into a folder named "short" and added to playback queue.
I merged this wav (using cox) several times into one larger wav file of ~48 seconds length and then into another one of ~96 seconds length, duplicated each of these files a few times and put them into folders "medium" and "long". I then queued up these folders to kodi's playlist and repeatedly played the 300 Hz sinus files for almost 45 minutes (weird experience by the way) while I tested almost any single option of Settings -> System -> Audio and Player Settings -> Music
After I finally found out, what causes all these tiny gaps and clicks, I tested this alot using many flac, wav and cbr+vbr mp3 files.
Solution:
In System settings > Audio you have to set resample quality to "Low (fast)" That's all. (For me myself there is absolutely no noticeable difference in audio quality if this option is set to "low" instead of higher values)
If this setting is set to "medium", some files still play gapless, some others don't.
If this setting is set to "high", almost any files won't play without gaps, especially if you play one large playlist containing many different file types of different folders as I mostly do.
With GPU setting it gets worst for me.
Furthermore I found out, really smooth playback isn't possible if crossfade is active and sample files are too short, so in my case the 9 second files don't produce gaps when played as is but will produce gaps and clicks when crossfade is set, the 48 second samples produce a short distortion which is hardly recognizeable and the longer the sample the shorter the distortion up to no longer recognizable under real world circumstances (playing real, longer songs).
I posted this solution here, because I don't know if this is a fixable bug or not.
If it is not a bug (thus not fixable) and all this is just because even rpi3 hasn't enough power to play audio gapless with higher resampling quality I think it then would be much better to have "resample quality: low" as default setting in upcoming raspberry pi builds so people no longer wonder what to do to make libreelec playing audio gapless, because I read almost a dozen of threads about kodi and gapless audio playback issues in this and other forums and none of the provided "solutions" like "flac is gapless, mp3 isn't, oh and you have to set output configuration to optimized man!" ever worked for me or the other thread openers (from what I know).
Since we all use the (almost) same piece of hardware, it can't just be me experiencing this.
I use libreelec on pi3 with hdmi audio output and I literally NEVER got accurate crossfading and gapless playback with libreelec until today. There was always an annoying little click and very short gap in the mid of the crossfaded portion. I wrote this twice before and that's been my prime reason, why I signed up to this forum (asking what is meant by paplayer being able to play gapless). There are many people reporting similiar things about gaps with kodi and never get a solution. Seems as if there just exist people who NEVER recognize gaps and clicks playing their audio tracks using kodi/libreelec on the one hand and those who ALWAYS have gaps and clicks (like me) on the other hand. Really odd.
Now for the very first time I got satisfying crossfading, even mixed between flac - mp3 vbr - mp3 cbr etc... And these annoying very short distortions which I had at the beginning of each track (independent to crossfade set or not) disappeared as well. Plus now my gapless concept albums (e.g. "Pink Floyd - The Wall" or "DJ Shadow - Live In Tune And On Time") eventually play gapless!
Here is what I've done:
I generated one ~9 second long 300 Hz sinus wav file. Wav because I wanted PCM as I couldn't believe all the comments in web, claiming lossy formats with variable bitrate causing these problems to be true. Yes, I know this can be part of the gapless issue, but some of my other almost 8 years old devices can play at least flac and constant bitrate mp3 gapless, while kodi for me didn't. I duplicated this wav file 9 times, put into a folder named "short" and added to playback queue.
I merged this wav (using cox) several times into one larger wav file of ~48 seconds length and then into another one of ~96 seconds length, duplicated each of these files a few times and put them into folders "medium" and "long". I then queued up these folders to kodi's playlist and repeatedly played the 300 Hz sinus files for almost 45 minutes (weird experience by the way) while I tested almost any single option of Settings -> System -> Audio and Player Settings -> Music
After I finally found out, what causes all these tiny gaps and clicks, I tested this alot using many flac, wav and cbr+vbr mp3 files.
Solution:
In System settings > Audio you have to set resample quality to "Low (fast)" That's all. (For me myself there is absolutely no noticeable difference in audio quality if this option is set to "low" instead of higher values)
If this setting is set to "medium", some files still play gapless, some others don't.
If this setting is set to "high", almost any files won't play without gaps, especially if you play one large playlist containing many different file types of different folders as I mostly do.
With GPU setting it gets worst for me.
Furthermore I found out, really smooth playback isn't possible if crossfade is active and sample files are too short, so in my case the 9 second files don't produce gaps when played as is but will produce gaps and clicks when crossfade is set, the 48 second samples produce a short distortion which is hardly recognizeable and the longer the sample the shorter the distortion up to no longer recognizable under real world circumstances (playing real, longer songs).
I posted this solution here, because I don't know if this is a fixable bug or not.
If it is not a bug (thus not fixable) and all this is just because even rpi3 hasn't enough power to play audio gapless with higher resampling quality I think it then would be much better to have "resample quality: low" as default setting in upcoming raspberry pi builds so people no longer wonder what to do to make libreelec playing audio gapless, because I read almost a dozen of threads about kodi and gapless audio playback issues in this and other forums and none of the provided "solutions" like "flac is gapless, mp3 isn't, oh and you have to set output configuration to optimized man!" ever worked for me or the other thread openers (from what I know).
Since we all use the (almost) same piece of hardware, it can't just be me experiencing this.
