RPi4 Video slows down after resolution change, only affects 1080p x264

Dragen · February 7, 2021 at 12:47 AM

After playing with the resolution when watching a 2160p x265 file, suddenly LibreElec (9.2.6) will have slowdowns and stuttering when playing many 1080p x264 files.

It is only the video that shows this, the audio plays fine.

While playing, the video will often slightly slow down and speed back up, or just stutter. When I seek (+-30 sek), the video will slow down to a point where it can be several seconds out of sync with the audio. If I pause at this point, the video will continue to play untill it catches up with the paused audio and then pause.

I've tried deinterlacing options, sync fps to monitor, etc. Nothing seems to fix it.

Debug log, path and filenames removed. I have added >>> marks to what files works and those that are problematic. I used files I know works and problematic.

I did notice that the bitrate for the 1080p that works fine is under 9000 kb/s bitrate, while the ones that doesn't are over 9000 kb/s. I can provide mediainfo for more specific data.

Dragen · February 10, 2021 at 12:09 AM

Updated main entry after poking around a lot more. It seems it only happens to 1080p x264.

mediainfo from file that works:

Code

Format                                   : Matroska
Format version                           : Version 4
File size                                : 2.90 GiB
Duration                                 : 44 min 22 s
Overall bit rate                         : 9 342 kb/s
Encoded date                             : UTC 2020-01-24 02:52:26
Writing application                      : mkvmerge v19.0.0 ('Brave Captain') 64-bit
Writing library                          : libebml v1.3.5 + libmatroska v1.4.8

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 44 min 18 s
Bit rate mode                            : Constant
Bit rate                                 : 8 711 kb/s
Nominal bit rate                         : 10 000 kb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.175
Stream size                              : 2.70 GiB (93%)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio
ID                                       : 2
Format                                   : E-AC-3
Format/Info                              : Enhanced AC-3
Commercial name                          : Dolby Digital Plus
Codec ID                                 : A_EAC3
Duration                                 : 44 min 18 s
Bit rate mode                            : Constant
Bit rate                                 : 640 kb/s
Channel(s)                               : 6 channels
Channel layout                           : L R C LFE Ls Rs
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 203 MiB (7%)
Language                                 : English
Service kind                             : Complete Main
Default                                  : Yes
Forced                                   : No

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mediainfo from problematic file:

Code

Format                                   : Matroska
Format version                           : Version 4
File size                                : 2.81 GiB
Duration                                 : 42 min 32 s
Overall bit rate                         : 9 471 kb/s
Writing application                      : mkvmerge v45.0.0 ('Heaven in Pennies') 64-bit
Writing library                          : libebml v1.3.10 + libmatroska v1.5.2

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 42 min 32 s
Bit rate mode                            : Constant
Bit rate                                 : 9 245 kb/s
Nominal bit rate                         : 10 000 kb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.186
Stream size                              : 2.75 GiB (98%)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio
ID                                       : 2
Format                                   : E-AC-3
Format/Info                              : Enhanced AC-3
Commercial name                          : Dolby Digital Plus
Codec ID                                 : A_EAC3
Duration                                 : 42 min 32 s
Bit rate mode                            : Constant
Bit rate                                 : 224 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 68.1 MiB (2%)
Language                                 : English
Service kind                             : Complete Main
Default                                  : Yes
Forced                                   : No

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**chewitt** · February 10, 2021 at 2:49 AM Official Post

There is no further development on LE 9.2 so best thing would be to switch to LE10 nightly images. They are quite stable for RPi4 now. The video driver stack is completely different so you might find new and exciting issues, but if you do, they may be fixed (unlike LE9.2 where they won't be).