This section configures the transcoding process.  The transcoding module converts all richmedia recordings and video uploads into h.264 mp4. After a recording is published or videos are uploaded an additional file called status.xml is placed in the same video folder.  


In the background the transcoder service will monitor for new status.xml files, or changes in existing files. New files will be picked-up and transcoded in the background. A log file transcoder-xxx.log will be created in each transcoded folder (xxx represent the video format). The default transcoding profile is set in Transcoding Status.



NOTE:  Be aware that transcoding all content will increase your disk usage!


The following sections will explain in more detail the parameters that can be set.


Max Worker Thread

By default the server will start-up a minimum of transcoding threads equal to the amount of server cores.  You can increase the number to speed-up the process. The service has a low priority so it will not interfere much with the other running processes.

Enable Process Timeout

Restrict single encoding jobs to a set time.

Transcoder option (Uploads)

Detailed transcoder commands used to determine the output audio and video codecs used for the manual video uploads.

Keep original Video  (Uploads)

Enable this check box if you want to store the original uploaded video format (e.g. avi, mpeg, mov etc). When the original is kept, future re-transcoding actions will use the original as input.

Transcoder option (Recordings)

Detailed transcoder commands used to determine the output audio and video codecs used for the automatic recorder uploads.

Keep original Video (Recordings)

Enable this check box if you want to store the original uploaded recording format. When the original is kept, future re-transcoding actions will use the original (video_post.mp4) as input.

Start date

All existing assets will be transcoded unless you force a start date.

Transcoder Retry Limit

Failed jobs will try a limited time to start.

Slide capture sensitivity

The transcoder can create index slides if the metadata of a recording has canvas and slide source set. Only the slide section will be scanned. Default settings is 8%. Higher values will create more index slides.

Slide detection frame rate (seconds)

To speedup the index creation and prevent too many slides during slide transitions we advise a frame rate of 1 frame per 2 seconds (0.5 fps, 30 frames per minute)

Show published recording in catalogue before being
transcoded

When this feature is enabled stream studio recordings will be instant available (before transcoding).
WARNING: Since native default recording bitrate is set to 8Mbps, instant playback might result in video buffering during playback for users with limited bandwidth.
We strongly advise not to enable this feature.



V5 transcoder scales much better over multiple cores that v4 did.

This means the number of concurrent jobs to be configured in General Settings/Transcoder Service/Max Worker Thread needs to be a lot lower than for v4.


Performance tests showed that when the number of cores is 8 or less, you should  not set the number of worker threads higher than 2.

A single job already saturates the cores to 100% but if that job would get stuck for some reason, no other jobs could be processed so set it to 2.

When using 16 cores, a single job can saturate the cores to about 70% so you would have benefit of running multiple jobs concurrently.

When you have 40 cores available (eg a dual XEON E5-2670V2 (2.5Ghz)), you could saturate the cores to 100% running 4 concurrent jobs.


The numbers above assume a Full HD input file transcoded to 3 bitrates at SD [756xauto] (700:64), HD [1280xauto](1500:96) and Full HD [1920xauto] (3500:128) (the number between () are video bitrate:audio bitrate).


Each transcoding job will consume 1.5GB of RAM. So when running 2 concurrent jobs, calculate for at least 3GB of RAM being used during transcoding.

When transcoding to 4K resolutions, the amount of memory used during transcoding will be even higher.

When the transcoding job has less memory available, transcoding performance will be considerably slower because of page-file swapping.


The test results below should give an indication of expected performance:


Profile 1: SD [756xauto] (700:64), HD [1280xauto](1500:96) and Full HD [1920xauto] (3500:128)

Profile 2: HD [1280xauto](1500:96) and Full HD [1920xauto] (3500:128)

Profile 3: Full HD [1920xauto] (3500:128)

Profile 4: HD [1280xauto](1500:96) 


Source file: 1 hour Full HD video at 30fps.


Results are in hh:mm:ss .


Cores/load

Concurrent Jobs

profile 1

SD/HD/FHD

profile 2

HD/FHD

profile 3

FHD

profile 4

HD

total transcoding time

4 cores (100%)

1

01:37:00

1:21:00

1:03:00

0:32:00

4:33:00

8 cores (100%)

1

0:51:00

0:41:00

0:30:00

0:18:30

2:20:30

16 cores  (70%)

1

0:44:00

0:29:00

0:19:00

0:21:00

1:53:00

40 cores (100%)

4

0:30:00

0:30:00

0:27:00

0:26:00

0:30:00