Conversion results are pretty strange

[User337 3]

Hello,

I already read up on this topic a bit and it seems that the bitrate you choose for conversion specifies rather a maximum bitrate than some value which will be aimed for in the converted file but I stil wonder if there is a way to get a different result than what I get:

 

I start with the following file:

The file is a MKV with 3.9 GB

 

I convert with the following settings:

Also I adjusted the transcoding settings for hevc since I read that lowering CRF can result in having a bitrate closer to what I initially entered (8 Mbps)

 

However after conversion I stil end up with the following:

A MKV with just 447.1 MB

 

The logs:

The call to ffmpeg is happening at 2024-07-09 14:45:58.567

The final result is afterwards transfered at 2024-07-09 15:41:06.409

embyserver.txtffmpeg-transcode-d582a8b8-132a-4570-a88c-19c951811766_1.txt

 

My question:

I like the conversion feature and want to use it further but what can I do about this extremely small file size?

[visproduction 315]

The original media has AC3 stereo and DTS surround.  Doesn't both audio tracks count into the bitrate conversion setting?  DTS is particularly intense to convert.  I see that the conversion speed wants to stay below 1.
 

Quote

14:46:44.345 elapsed=00:00:45.36 frame=  970 fps= 21 q=36.0 size=   11264kB time=00:00:40.39 bitrate=2284.5kbits/s throttle=off speed=0.89x    

...

14:46:50.805 elapsed=00:00:51.80 frame= 1138 fps= 22 q=36.0 size=   12800kB time=00:00:47.47 bitrate=2208.9kbits/s throttle=off speed=0.916x    

...

14:47:11.153 elapsed=00:01:12.17 frame= 1714 fps= 24 q=36.0 size=   16896kB time=00:01:11.44 bitrate=1937.3kbits/s throttle=off speed=0.99x    
 

Is the video conversion limited that it must happen below a speed of 1.0 for all conversions so that the playback is possible?  If this is true, then isn't the CPU and conversion speed limited so that the playback is in real time and video just happens to only be no more then 1 mbps because the DTS and AC3 audio also have to happen in real time?  I don't know if this is how it works.  It would seem that the server's ability to process HEVC video + 2 audio streams and keep in in real time, so that the user's can view the movie without buffering and pausing.  Then the problem is the server is not fast enough to handle converting all three at once.  If no one uses Surround sound, maybe remove the DTS from the master media and see that helps the video get a higher bitrate.  I don't do transcoding at all.  This is just a guess.

[Luke 42080]

The software encoders can often produce bitrates that are far lower than the requested max rate, whereas the hardware encoders generally come much closer. So we probably need to look at that.

But keep in mind converting h264 to hevc so you can achieve the same quality at a lower bitrate.

[User337 3]

3 hours ago, Luke said:

The software encoders can often produce bitrates that are far lower than the requested max rate, whereas the hardware encoders generally come much closer. So we probably need to look at that.

But keep in mind converting h264 to hevc so you can achieve the same quality at a lower bitrate.

But is it really realistic in my case? A file shrinking from 4gb to under 1gb? I know that hevc produces way smaller files having the same quality than bigger files in h264 but is the difference really that big? Sadly hardware encodes are no solution for me atleast for the moment.

 

On 7/9/2024 at 9:56 PM, visproduction said:

The original media has AC3 stereo and DTS surround.  Doesn't both audio tracks count into the bitrate conversion setting?  DTS is particularly intense to convert.  I see that the conversion speed wants to stay below 1.
 

Is the video conversion limited that it must happen below a speed of 1.0 for all conversions so that the playback is possible?  If this is true, then isn't the CPU and conversion speed limited so that the playback is in real time and video just happens to only be no more then 1 mbps because the DTS and AC3 audio also have to happen in real time?  I don't know if this is how it works.  It would seem that the server's ability to process HEVC video + 2 audio streams and keep in in real time, so that the user's can view the movie without buffering and pausing.  Then the problem is the server is not fast enough to handle converting all three at once.  If no one uses Surround sound, maybe remove the DTS from the master media and see that helps the video get a higher bitrate.  I don't do transcoding at all.  This is just a guess.

thank you for your comment. I will need to reread a few times when im at home to understand it

[Luke 42080]

1 minute ago, User337 said:

But is it really realistic in my case? A file shrinking from 4gb to under 1gb? I know that hevc produces way smaller files having the same quality than bigger files in h264 but is the difference really that big? Sadly hardware encodes are no solution for me atleast for the moment.

Yes I agree it is an extreme example, so while there should be some reduction in size, it shouldn't be that much.

[User337 3]

2 hours ago, Luke said:

Yes I agree it is an extreme example, so while there should be some reduction in size, it shouldn't be that much.

Yeah for sure. For the moment I decided to just convert to h264 which is also totally fine for full hd with about 6 Mbps and also direct plays on more devices. if you happen to need more details or something else just ping me here but for the moment I am fine.