PGS Subs embedded my MKVs get misplaced after hardware transcoding

[Nauclerus 1]

I've downloaded the latest and set up the Emby Server (Docker) environment and I've been thoroughly enjoying this wonderful application so far. I was using muxed MKVs with embedded subs (PGS) and it all worked perfectly. Direct play in 4K and Software Transcoding worked fine, both displayed the embedded subs perfectly well. I'll use Oppenheimer here as an example.
(Subs here are located slightly to the left of the frame, that's due to the subs included and not a fault on Emby's part.)

 

Of course when I confirmed all worked well, I had to try out Hardware encoding for more powerful conversion and the possibility for friends and family to access my repository remotely.
Now I noticed multiple "shortcomings" that came with this:
- A noticable green hue (compare the two images), alltough this might the fault of wrongly transcoded DV HDR filter (doing research on that)

- When using the embedded subs (preferable due to perfect audio timing), I notice that when HARDWARE trancoding specifically, the subs seem to get misplaced, seemingly in the 1920x1080 quadrant of a 4k frame... but that is indeed very strange behaviour.

 

Both transcode logs are included, aptly named. 

I will add that while both are pretty big downfalls, mostly the subtitle problem is actually dealbreaking as most of my users will need subtitles.
I tried to download SRT subtitles as a substitution, that resulted in the following on the Web Client:

 

The green hue remains, but the SRT subs are correctly displayed in the Web Client, Huzzah! I test on the Windows Theather app:

 

Nothing... And the hue persists also here. When I try to get the PGS subs to work in here after a 4k > 1080p transcode just like in web player, they seems to shift to the wrong place.
Of this last two screenshots there's also a ffmpeg log included, aptly named.

I will admit that I've searched on this topic for quite a bit allready and nothing seems to resolve the subtitles missing or being misplaced. Is this a known issue? Has this been seen before? Any help would be GREATLY appreciated!

Regards,

 

Nauclerus

 

ffmpeg-transcode-hardware.txt ffmpeg-transcode-software.txt ffmpeg-transcode-hardware-STRinEmbyTheaterDesktop.txt ffmpeg-transcode-hardware-SRTinWebClient.txt

[Luke 37106]

Hi, we are looking into this. Thanks for reporting.

[Nauclerus 1]

Thank you Luke, it's greatly appreciated. 
If it helps you in any way, within the ffmpeg logs I've noticed that a certain line indicates that something is missing. 
```

12:35:46.738 ffmpeg version 5.1-emby_2023_06_25 Copyright (c) 2000-2022 the FFmpeg developers and softworkz for Emby LLC

12:35:46.738 built with gcc 10.3.0 (crosstool-NG 1.25.0)

12:35:46.738 Execution Date: 2024-04-21 12:35:46

12:35:47.152 [matroska,webm @ 0x1476040] Could not find codec parameters for stream 2 (Subtitle: hdmv_pgs_subtitle (pgssub)): unspecified size

Consider increasing the value for the 'analyzeduration' (0) and 'probesize' (5000000) options

```

All the PGSsubs have this "error" and it attracted my attention concerning the weird placement of these subs (this excerpt was from the last included log)

[Happy2Play 8296]

Devs will know more but I used the diagnostic plugin and replaced canvas corrected the position issue in my test.

Like a scaling mismatch

 

Examples above

>>>>>>  Subtitle Processing Steps for [0:2]: HDMV PGS subtitles
        Step                    Format             Target Size 
        HDMV_PGS_SUBTITLE    >> Subs: Bitmap                   
        scale                >> Video: UNKNOWN     1920x1080 

>>>>>>  Video Processing Steps for [0:0]: H.265 (HEVC)
        Step                    HW-Context   Format       SW-Format           Size   Next
        HEVC                 >> CUDA         cuda         yuv420p10      3840x2160 >> scale_cuda
        scale_cuda           >> CUDA         cuda         yuv420p10      1920x1080 >> setsar
        setsar               >> CUDA         cuda         yuv420p10      1920x1080 >> setparams
        setparams            >> CUDA         cuda         yuv420p10      1920x1080 >> tonemap_cuda
        tonemap_cuda         >> CUDA         cuda         yuv420p        1920x1080 >> setparams
        setparams            >> CUDA         cuda         yuv420p        1920x1080 >> hwdownload
        hwdownload           >> -            yuv420p      yuv420p        1920x1080 >> format
        format               >> -            yuv420p      yuv420p        1920x1080 >> format
        format               >> -            yuv420p      yuv420p        1920x1080 >> overlay
        overlay              >> -            yuv420p      yuv420p        1920x1080 >> 

 

11:53:17.335   Stream #0:0: Video: hevc (Main 10), yuv420p10le(tv, bt2020nc/bt2020/smpte2084), 3840x2160 [SAR 1:1 DAR 16:9], Level 153, 23.98 fps, 23.98 tbr, 1k tbn (default)
11:53:17.335     Metadata:
11:53:17.335       BPS             : 61451857
11:53:17.335       DURATION        : 03:00:22.187000000
11:53:17.335       NUMBER_OF_FRAMES: 259473
11:53:17.335       NUMBER_OF_BYTES : 83130436755
11:53:17.335     Side data:
11:53:17.335       DOVI configuration record: version: 1.0, profile: 8, level: 6, rpu flag: 1, el flag: 0, bl flag: 1, compatibility id: 1
11:53:17.335   Stream #0:1(eng): Audio: dts (DTS-HD MA), 48000 Hz, 5.1(side), s32p (24 bit) (default)
11:53:17.335     Metadata:
11:53:17.335       title           : DTS-HD MA 5.1
11:53:17.335       BPS             : 3566822
11:53:17.335       DURATION        : 03:00:22.155000000
11:53:17.335       NUMBER_OF_FRAMES: 1014577
11:53:17.335       NUMBER_OF_BYTES : 4825087720
11:53:17.335   Stream #0:2(eng): Subtitle: hdmv_pgs_subtitle, 3840x2160

 

11:53:17.553 subtitle input filter: decoding size 3840x2160
11:53:17.553 Auto-inserting subfeed filter
11:53:17.553 Auto-inserting graphicsub2video filter
11:53:25.617 Output #0, segment, to '/storage/temp/transcoding-temp/C5AD24/C5AD24_%d.ts':
11:53:25.617   Metadata:
11:53:25.617     encoder         : Lavf59.27.100
11:53:25.617   Stream #0:0: Video: h264 (High), yuv420p(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 14616 kb/s, 23.98 fps, 90k tbn

 

[Nauclerus 1]

@Happy2PlayThank you very much for your input, you've let me discover this nice plugin, lots of handy buttons and switches indeed.

I've been tinkering this morning and at one point I succeeded in getting the subtitles right! Unfortunately in all my enthusiasm I rebooted the server to verify and wiped my diagnostics settings with it. I also can't seem to find thew exact ffmpeg log wherein it worked, I can only blame myself.

Nevertheless I've been pouring over logs and even in instances where it isn't correctly displayed, the logs are pretty similar to your excerpts:

 

Quote

>>>>>> Subtitle Processing Steps for [0:2]: HDMV PGS subtitles

Step Format Target Size

HDMV_PGS_SUBTITLE >> Subs: Bitmap

scale >> Video: UNKNOWN 1920x1080

 

>>>>>> Processing Plan

Name CanDoInHW WillDoInHW Reason

NVDEC Quadro P2000 - H.265 (HEVC) >> True True Hardware Codec

VideoInput >> True True Matching hardware context

Scaling >> True True

ToneMapping (when possible) >> True True

SubtitleOverlay >> False False

VideoOutput >> True True Hardware encoder

NVENC Quadro P2000 - H.264 (AVC) >> True True Hardware Codec

 

>>>>>> Video Processing Steps for [0:0]: H.265 (HEVC)

Step HW-Context Format SW-Format Size Next

HEVC >> CUDA cuda yuv420p10 3840x2160 >> scale_cuda

scale_cuda >> CUDA cuda yuv420p10 1920x1080 >> setsar

setsar >> CUDA cuda yuv420p10 1920x1080 >> setparams

setparams >> CUDA cuda yuv420p10 1920x1080 >> tonemap_cuda

tonemap_cuda >> CUDA cuda yuv420p 1920x1080 >> setparams

setparams >> CUDA cuda yuv420p 1920x1080 >> hwdownload

hwdownload >> - yuv420p yuv420p 1920x1080 >> format

format >> - yuv420p yuv420p 1920x1080 >> format

format >> - yuv420p yuv420p 1920x1080 >> overlay

overlay >> - yuv420p yuv420p 1920x1080 >>

Quote

09:25:32.154 subtitle input filter: decoding size 3840x2160
09:25:32.154 Auto-inserting subfeed filter
09:25:32.154 Auto-inserting graphicsub2video filter
09:25:40.245 Output #0, segment, to '/storage/temp/transcoding-temp/297BD4/297BD4_%d.ts':
09:25:40.245   Metadata:
09:25:40.245     encoder         : Lavf59.27.100
09:25:40.245   Stream #0:0: Video: h264 (Main), yuv420p(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 14616 kb/s, 23.98 fps, 90k tbn
09:25:40.245     Metadata:
09:25:40.245       encoder         : Lavc59.37.100 h264_nvenc
09:25:40.245     Side data:
09:25:40.245       cpb: bitrate max/min/avg: 14616000/0/14616000 buffer size: 29232000 vbv_delay: N/A
09:25:40.245   Stream #0:1(eng): Audio: ac3, 48000 Hz, 5.1, fltp, 384 kb/s (default)
09:25:40.245     Metadata:
09:25:40.245       encoder         : Lavc59.37.100 ac3

 

Despite this, the subtitles remain incorrectly displayed in the top-left quadrant

[Nauclerus 1]

@Happy2Play@Luke

It seems I've been a little bit of an idiot concerning the -canvas_size:s:1 substitution... As I inspected the used ffmpeg command in my logs, I noticed that it contained -canvas_size:s:0 instead of -canvas_size:s:1. After changing that in command substitution using the Diagnostic plugin I can now reliably get the subtitles to show up correctly.
Log attached of a successful encode using these options. 

Thank you so very much for this! This allows the server to be used for it's intended purpose for now at least, until Luke and the team find a solution to this problem. 

ffmpeg-transcode-Diagnostic_Resize_Works.txt