Wrong Bitrate on Live TV streamed by TBS encoder

[vaiuba 0]

Hello,

I've a TBS encoder with 2 Streams:

1) 1080p H265 7.000 kb/s bitrate

2) 720p H265 2.000 kb/s bitrate

If I connect to TBS using VLC I can see all the time the current bitrate corresponds to what set in TBS Encoder.

 

When I open Live TV connected to this live stream with any device using Emby app, I can see different bitrate:

1) 15Mbits

2) 6Mbits

This causes troubles when watching in a limit bandwith situation, where I set up a max 5MB/s in the Emby app option. In these cases Emby force transcoding on stream 2), which is bad.

Is there any chance to force Emby to read correct bitrate?

Thank you

 

[Carlo 4552]

It could be the client you're using can't play back the container or video codec so it needs to transcode.  In that case it will need transcode the video to h.264 which will require more bits.

May I suggest a quick test.  For the first test remove the sub stream encoding and just use the main stream.

Try that and see if it makes a difference with only 1 stream being generated.

The second test you can try is to switch the profile being used from H.265 to H.264.

Let us know what you get after trying both of these.

 

[vaiuba 0]

Thank you for your reply.

I already tried to change encode profile, but it is the same.

If I put the maximum bandwith to a value > 6Mbps (10Mbit for example) no transcode is done. This happen just when I set a value that is lower than read bitrate (which is unfortunately wrong).

How Emby calculate this value? If I ffprobe the source stream, i can see on bit_rate field the value N/A (there is now way to explicit set a value in the stream property).

thank you

[Carlo 4552]

Did you try the first thing I mentioned removing the sub stream?

What does the client show when playing back with the H.264 profile?

[vaiuba 0]

Switched to h264 and disabled substream.

Same thing. Main stream is read by Emby with a 15Mbps bitrate.

attached TBS configuration and stats for nerds

[Carlo 4552]

Thanks for trying that.  Your results are interesting.

Do you get different results with different Emby Clients?

If you do a small 5 minute recording and then play that back, what bitrate does it show?

[vaiuba 0]

Sorry for delay, I had some troubles adding fake EPG in order to enable recording.

This is current bitrate for stream 2)

 

Any Ideas?

[Carlo 4552]

That looks about right to me for a 2K setting for bitrate.

What does MediaInfo show for this file?
https://mediaarea.net/en/MediaInfo

[vaiuba 0]

This is how Mediainfo shows

[Carlo 4552]

OK so that is in agreement with Emby.  Have you tried this with the primary stream?

[vaiuba 0]

Same, recording bitrate matches Original stream bitrate, but not Emby Live Bitrate

[pünktchen 1350]

Try to change the encoder setting from variable to constant bitrate. I guess ffmpeg cannot read the overall variable bitrate as long as the file/stream has not finished and so Emby will just use some default values depending on the resolution.

Edited July 19, 2021 by pünktchen

[vaiuba 0]

I already tried to change all parameters on TBS Encoder, restarted Emby everytime, but nothing changes.

[pünktchen 1350]

But my other assumption still stands:

3 hours ago, pünktchen said:

I guess ffmpeg cannot read the overall variable bitrate as long as the file/stream has not finished and so Emby will just use some default values depending on the resolution.

I have exerienced similar recently with Handbrake and the Quicksync encoder. Even MediaInfo did not show any bitrate until the encoding has finished.

[vaiuba 0]

I tried ffprobe to the stream and bit_rate is "N/A"

Any idea how to fix it?

[Carlo 4552]

Maybe, using constant bit rate for the encode would help.

[vaiuba 0]

I set CBR on TBS Encoder, restarted Emby, but bitrate is always read as 15 Mbits for 1) and 6Mbits for 2)

ffprobe still reads bit_rate = N/A

Edited July 20, 2021 by vaiuba

[Carlo 4552]

It sounds like the encoder is fully writing header information so Emby doesn't have a way to accurately determine the bitrate and has to guess.  If it does that it will opt on the side of safety and assume a higher bitrate.

Which specific encoder are you using?

[vaiuba 0]

This is the product I use:

https://www.tbsdtv.com/products/tbs2603se_professional_hd_h265_or_h264_hdmi_video_encoder.html