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1. Embed this notice
   jwz (jwz@mastodon.social)'s status on Wednesday, 28-May-2025 16:19:57 JST jwz

   RTMP / HLS segment corruption.

   Dear Lazyweb, When my internal video encoder machine relays its RTMP stream to the external public server, MPEG glitches get introduced, and I would like to know how to fix that. I am hoping for answers from someone who...
   https://jwz.org/b/ykoc

   • Embed this notice
     Peter Krefting (nafmo@social.vivaldi.net)'s status on Wednesday, 28-May-2025 16:19:56 JST Peter Krefting

     in reply to

     @jwz Does your RTMP source create IDR frames in the H.264 stream? If not, the segmenter might be splitting on keyframes that are needed by the previous segment.

     Looking at the ext/1748393061627.ts, ffmpeg reports that it is not starting with a proper keyframe, which could definitely lead to problems on playback.

     (At $DAYJOB, I write software that can monitor both RTMP and HLS, but it is probably overkill for your application: <http://www.bridgetech.tv>/).

   • Embed this notice
     jwz (jwz@mastodon.social)'s status on Wednesday, 28-May-2025 17:01:29 JST jwz

     in reply to

     • Peter Krefting

     @nafmo I don't have the slightest idea. The "int" files were created by OBS and sent to nginx. The "ext" files were sent from nginx to nginx. I don't know how the frames in the segments get split and recombined, but I am pretty sure they are not re-encoded.

   • Embed this notice
     Peter Krefting (nafmo@social.vivaldi.net)'s status on Wednesday, 28-May-2025 17:01:29 JST Peter Krefting

     in reply to

     @jwz Right. I don't have much experience at that end of the chain; I briefly looked at the help pages for OBS but couldn't find any references to IDR or EBP for segmenting.

     What are you using to create the H.264 RTMP stream in the first place? Does it have a setting to generate IDR frames?

     Also, RTMP is an old and underspecified protocol that was used with Adobe Flash; can your encoder output MPEGTS multicasts or something else more modern that OBS can ingest? Does it support inserting EBP (Encoding Boundary Point) markers?

   • Embed this notice
     jwz (jwz@mastodon.social)'s status on Wednesday, 28-May-2025 18:17:36 JST jwz

     in reply to

     • Peter Krefting

     @nafmo OBS is not ingesting, it is creating. OBS -> nginx RTMP creates the TS files in the "int" directory which seem fine. Then nginx -> other nginx creates the files in the "ext" directory which seem not. I linked to the doc for the nginx RTMP plugin which also doesn't mention IDR frames, but that is sensible since as far as I am aware moving MPEG frames over RTMP *does not create new frames*.

     "RTMP is old and busted, go find something else" is not what I find a compelling argument.

   • Embed this notice
     Peter Krefting (nafmo@social.vivaldi.net)'s status on Wednesday, 28-May-2025 18:17:57 JST Peter Krefting

     in reply to

     @jwz I'm just trying to understand your setup. Where is the video stream coming from, initially?

     I didn't mean to come off sounding rude, but after 10+ years writing software monitoring RTMP, it is not something I would recommend anyone to use. It's probably not the culprit in this scenario, though.

   • Embed this notice
     Peter Krefting (nafmo@social.vivaldi.net)'s status on Wednesday, 28-May-2025 18:29:49 JST Peter Krefting

     in reply to

     @jwz Sorry, I was not meaning to sound rude, but after 10+ years on writing software to monitor RTMP, it is not something I recommend using, that's why I asked if another transport could work.

     I was trying to understand the setup; what the original video source was and where the segmenting happened. Having the segmentation as close to the encoder as possible is usually better.

     HLS segments need to be playable separately, which is why they should be cut at IDR frames; EBP is a way to signal those cutting points, but having IDR frames in the source stream ought to be enough.