[FFmpeg-user] Warning : Thread message queue blocking

Moritz Barsnick barsnick at gmx.net
Thu Jun 21 11:17:58 EEST 2018

On Wed, Jun 20, 2018 at 15:41:58 +0000, yael Laouar wrote:

(Please avoid top-posting on this list.)

A lot of your questions are much easier to answer if you show us your
(actual) ffmpeg command line and its complete, uncut console output.

> You're meaning that if I raise the value, it'll simply extend the
> live stream duration without but problem but there's gonna be a
> problem at a time ?

Probably. If ffmpeg's stats output reports a processing "speed" of less
than 1x, you're lost with your current settings. But see below.

> The fact is I'm already using the preset configuration ultrafast, I
> can't go any faster. And when you say lower resolution, you mean the
> ffmpeg input resolution before transcoding ? Because I can't change
> that, I'm retrieving frames from the RICOH THETA V and it's 4k.

Hmm, the datasheet I found says:
> File size and frame rate (live streaming):
> 3840 × 1920, 29.97 fps
> 1920 × 960, 29.97 fps


> Speaking about speed indicator : during my stream my value is near
> constant at speed=0,999. Is that an acceptable value or this 0,001
> will add a mini slowdown to the video ? Will, adding -re option,
> force the speed to 1 withtout drawbacks ?

No, that's probably slight variation and should be okay. Depending on
the input format, "-re" might not change anything, but it probably
doesn't hurt. (I'm saying: I don't know.)

If you go from "ultrafast" to "fast" and still achieve ~1x, you're
okay. You can check how fast the pure decoding goes as such:

$ ffmpeg -i input_url -f null -

Additional question: Does this also give you issues with the thread cue

> ffmpeg -thread_queue_size 512 -f avfoundation -i "0:" -thread_queue_size 2048 -f avfoundation -i ":4" -crf 30 -preset ultrafast -strict experimental -vf scale=1920:960 -vcodec libx264 -tune zerolatency -pix_fmt yuv420p -r 30 -g 60 -threads 4 -acodec aac -ac 4 -b:a 512k -map_channel 1.0.0 -map_channel 1.0.1 -map_channel 1.0.2 -map_channel 1.0.3 -map 0:v -map 1:a -f flv rtmp://localhost/live_no_1/mon_flux

> -vf scale=1920:960
If you manage to set the camera to deliver 1920x960 (and its rescaled
quality is acceptable), you don't need your CPU to do rescaling. OTOH,
your processing speed looks fine, in summary.

The rest I can't comment on.


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