[Jim Sustacek]

The iPhone trimming may not actually be trimming the audio/video data, just marking trim points that FFMPEG may not understand.

I would try re-doing the trimming with FFMPEG too. For example, in FFMPEG, “-ss 10” will start the new transcoded file after 10 seconds, and “-t 21” will trim it after 21 seconds. Adjust those values as needed (you may be able to find them in your FFPROBE output, otherwise you may have to view the file and/or experiment with different values).

[Jim Sustacek]

Can you share the complete FFMPEG command, as generated by ASP.NET? That way, we can test it on our versions of FFMPEG. A link to download a sample video might help, too.

Also, if you are running Windows, have you tried the Zeranoe builds of FFMPEG?

https://ffmpeg.zeranoe.com/builds/

[Jim Sustacek]

In my experience, Media Express is very picky about what it plays back. Basically, it has to be recorded using Media Express.

The actual hardware is not so restrictive, however, if you’re just looking to send video out on the Blackmagic output. If you can find a way to use bmdtools (Linux or Mac only, unfortunately), you can use FFMPEG to pipe pretty much anything out on it using bmdplay:
https://forum.blackmagicdesign.com/viewtopic.php?f=4&t=3349#p20332

[Jim Sustacek]

[EricBowen] “Media Express allows more than 1 instance but you have to launch it again each time by creating separate exe files for Media Express if I remember it correctly. “

Just tried it on my Mac (duplicated the app to “Blackmagic Media Express copy”), started capturing each card separately, and it appears to work.

Could have sworn I tried this before and had issues, although maybe I am confusing it with Wirecast (I know Media Express won’t work if Wirecast is open, etc.). If this indeed works, it’s a much better solution than bmdcapture (for those looking for multiple captures but do not need streaming capabilities).

[Jim Sustacek]

[Andre van Berlo] “Actually I own wirecast pro since a couple of days so this would be good news. Is the video quality of each camera capture as good as what I can record in the camera’s internally on SD cards? “

In my experience, no. Recording through Wirecast gives a softer, fuzzier image than recording directly through Media Express.

A nice advanced solution (especially for scripting capture) is using the command line bmdtools utilities, specifically bmdcapture coupled with ffmpeg:
https://github.com/lu-zero/bmdtools

Downside to that is no GUI and no preview window, although you can stream the ffmpeg output to local RTP ports and monitor it using QuickTime Player or ffplay (with a 2-3 second delay).

[Jim Sustacek]

Are you just recording to the iMac’s standard SATA internal hard drive? If so, that may be your bottleneck, at least for fully uncompressed video recording from Blackmagic products. Run the “Blackmagic Disk Speed Test” that’s included in the Intensity driver/software install and post the results here.

In my case, I installed the Apple ProRes codecs and switched to recording in ProRes LT which was sufficient for my needs:
https://www.jonathangrubbs.com/journal/pro-quicktime-codecs-no-fcp/

Otherwise, you will probably need a SSD or external Thunderbolt drive for fully uncompressed recording.

[Jim Sustacek]

In my experience with Blackmagic Intensity products, Media Express could only run one instance, accessing one device.

Wirecast allows multiple instances, though, and each instance can be set up to access a different device.

[Jim Sustacek]

What’s your working rtmpdump command? It sounds like the RTMP server requires this security token. Can it simply be passed as part of the RTMP URL?

[Jim Sustacek]

I guess my original rationale was that I could transcode with one process, and then just segment with the other. But I suppose you could easily combine them. Of course, if your source stream is already H.264/AAC, maybe you could eliminate the transcoding altogether?

If the original poster wants to expand upon his purpose, that might help too.

[Jim Sustacek]

Here’s what I’ve used:

ffmpeg -loglevel quiet -i rtmp://flash.server.com/vod/_definst_/streamname -c:v libx264 -profile:v baseline -level 3.1 -c:a aac -strict experimental -f mpegts - | ffmpeg -i - -c copy -map 0 -f segment -segment_list ffmpeg.m3u8 -segment_format mpegts -segment_time 10 ffmpeg%03d.ts

I haven’t really used it live, but I assume if you write those files (.m3u8 and .ts) to a public web server directory, you can embed that .m3u8 file or just link it directly for iOS devices.