Transcoding due to subtitles

[atgomez6555 0]

Hello,

I am trying to stream a show with PGSSUB on Google Chrome in my browser. I understand Chrome does not support PGSSUB, so the fact that transcoding is happening is not the issue. The issue is no matter what settings I choose, it will only transcode at 2-2.7 mbps bitrate. The media itself is 30 mbps, and I am on a local ethernet connection. I have no profile settings restricting transcoding, and "normal" transcoding off network allows me to change bitrate. It seems to be an issue specific to the forced transcoding due to subtitles that makes it transcode at such a low bitrate.

[Luke 42080]

Hi there, can we please look at an example? Thanks.

[Carlo 4561]

@atgomez6555 Can we get more info please?

[atgomez6555 0]

8 hours ago, cayars said:

@atgomez6555 Can we get more info please?

What specific information do you need? I have also noticed this same issue with HEVC codec in Chrome on Windows 10, where the transcoding only occurs at ~2.5 Mbps. It's all videos of either HEVC or PGSSUB subs.

[Luke 42080]

Please provide the information requested in how to report a media playback issue. thanks.

[atgomez6555 0]

12 minutes ago, Luke said:

Please provide the information requested in how to report a media playback issue. thanks.

Is there a way to upload the logs in which only Admins can see them? So random people can't see my server address in the logs.

[atgomez6555 0]

I just did a find a replace for my server name. 2 of the transcodes are from HEVC, 1 is PGSSUB.

ffmpeg-transcode-40f4b252-4805-4ca1-ba86-372f533ffc40_1.txt ffmpeg-transcode-30506e34-a743-408c-a867-d0b6144ec468_1.txt ffmpeg-transcode-391f3c55-fbcf-48ba-9f26-4e8012e49194_1.txt embyserver.txt

[Carlo 4561]

In Chrome under playback menu options what do you have setup for Home network quality:?

Is this playing back from your own lan where the server resides?

[atgomez6555 0]

21 hours ago, cayars said:

In Chrome under playback menu options what do you have setup for Home network quality:?

Is this playing back from your own lan where the server resides?

Is it on my own LAN, ethernet 10G connection to server from desktop. I'm not sure what you mean by playback menu options for Chrome.

[pwhodges 2012]

He means in Emby, running in Chrome. 

Paul

Edited December 4, 2020 by pwhodges

[atgomez6555 0]

Ah in that case it is set to auto. But nothing changes even if I manually set playback to a specific bit rate during play - it stays fixed at the ~2.5 mbps bit rate even if I select 15mbps for a 20mbps movie. The fact that it already is auto transcoding because of Subs or Codec seems to override my selection.

[Carlo 4561]

It's also quite possible that 2.5mbps is all the bitrate that's needed when it converts.  

[atgomez6555 0]

4 hours ago, cayars said:

It's also quite possible that 2.5mbps is all the bitrate that's needed when it converts.  

That's not that case as the quality is drastically reduced. It is transcoding a 20 Mbps bit rate movie to a 2.5 Mbps stream. Almost a 10x reduction.

[Carlo 4561]

1 hour ago, atgomez6555 said:

That's not that case as the quality is drastically reduced. It is transcoding a 20 Mbps bit rate movie to a 2.5 Mbps stream. Almost a 10x reduction.

I'd like to see this first hand if possible which may be much easier. There are numerous things that could cause low bitrate transcodes but I can usually spot//find them quickly in real-time. Can we setup a remote session using TeamViewer some time over the weekend (or whenever convenient for you) where I login to your desktop and we work together on the problem? You can then demonstrate it first hand to me and we can review/test any possible config changes that might help?

Worse case, I can't help you, but can grab info and logs to directly give to devs and make a case for you from first hand experience.

Carlo

[Luke 42080]

I don't think a teamviewer session is necessary. We're passing in a maxrate of 20 mbps to the ffmpeg encoder, and the output just ends up being much lower than that.

@softworkz can help explain why that can happen sometimes.

[Carlo 4561]

On 12/4/2020 at 11:07 PM, atgomez6555 said:

That's not that case as the quality is drastically reduced. It is transcoding a 20 Mbps bit rate movie to a 2.5 Mbps stream. Almost a 10x reduction.

And that's going from HEVC to AVC as well which would normally require more bitrate, not less to hold the same quality. Certainly not 1/10 but more likely 2 to 3x.

@Luke Do you see the 20Mbps in those ffmpeg logs from the hevc files?  I'm not seeing it but far lower max rates which would explain what he's seeing.

That's why I wanted to take a look.

[Happy2Play 9782]

19 minutes ago, cayars said:

Do you see the 20Mbps in those ffmpeg logs from the hevc files?  I'm not seeing it but far lower max rates which would explain what he's seeing.

That's why I wanted to take a look.

from ffmpeg-transcode-391f3c55-fbcf-48ba-9f26-4e8012e49194_1.txt

Capability

VideoBitrate=19808000&AudioBitrate=192000

Item bitrate

"Bitrate":19784405

reason

TranscodeReasons=SubtitleCodecNotSupported

command snippet

-c:v:0 libx264 -g:v:0 72 -maxrate:v:0 19784405 -bufsize:v:0 39568810


19:38:45.759   Metadata:
19:38:45.759     encoder         : Lavf58.35.100
19:38:45.759     Stream #0:0: Video: h264 (libx264), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 23.98 fps, 90k tbn, 23.98 tbc (default)
19:38:45.759     Metadata:
19:38:45.759       encoder         : Lavc58.62.100 libx264
19:38:45.759     Side data:
19:38:45.759       cpb: bitrate max/min/avg: 19784000/0/0 buffer size: 39568000 vbv_delay: N/A

But ends up with about 2.5

19:39:40.507 [libx264 @ 0x1aa07c0] kb/s:2334.45

 

Edited December 13, 2020 by Happy2Play

[Carlo 4561]

Thanks Happe2Play, I didn't look at the second.  So this time looked at all 3.

1st file:
"Codec":"hevc"
"BitRate":3583250,"BitDepth":10
VideoBitrate=139808000&AudioBitrate=192000
[libx264 @ 0x22f7380] kb/s:2422.01

2nd file:
"Codec":"hevc"
"BitRate":3583250,"BitDepth":10
VideoBitrate=19808000&AudioBitrate=192000
[libx264 @ 0x1a8cf40] kb/s:2516.47

3rd file:
"Codec":"h264"
"BitRate":19784405,"BitDepth":8
VideoBitrate=19808000&AudioBitrate=192000
[libx264 @ 0x1aa07c0] kb/s:2334.45

Looking at the 2nd and third file for example I wouldn't expect to get a similar output bitrate.

[softworkz 5070]

@atgomez6555 - What happens when you set CRF to 18 and preset to "very slow" in the transcoding settings?

[atgomez6555 0]

@softworkz So that did improve it. I have attached logs from the PGSSUB file. The previous settings were CRF 23, and AUTO. The stats popup shows way higher spikes than before for the bit rate value, and seems to hang around 8.7 Mbps.

ffmpeg-transcode-8cfc8d2e-db7a-4008-b025-78d49d98213a_1.txt

Edited December 14, 2020 by atgomez6555

[softworkz 5070]

@atgomez6555 - Thanks for the feedback!

I you want to experiment a bit more, you can take a look at this conversation: