[FFmpeg-user] Impossible to convert between the formats supported by the filter 'Parsed_null_0' and the filter 'auto_scaler_0'

James Girotti james.girotti at gmail.com
Tue Feb 13 20:56:17 EET 2018

> Recently, I faced transcoding issues with fully hardware nvdec/nvenc
> scheme. Particularly, my FFmpeg feed fails with the following error after
> 30-60 minutes of live transcoding:

I have recently encountered this as well, but with DVD video material.

> As I understand, some parameters change after 30-60 minutes in video
> stream and FFmpeg tries to use software scaler in fully hardware scheme.
> But I can't figure out exact reasons to act against the problem. I will be
> very grateful if someone could direct me. I use following cmd line:
> ---
> /usr/local/ffmpeg/bin/ffmpeg -analyzeduration 100M -probesize 100M
> -loglevel debug -hwaccel_device 1 -hwaccel cuvid -c:v h264_cuvid -deint 2
> -drop_second_field 1 -i udp://
> e=250000&overrun_nonfatal=1 -map p:1011:0 -map p:1011:1 -c:v h264_nvenc
> -profile:v high -level 4.1 -b:v 2048k -c:a libfdk_aac -b:a 128k -af
> aresample=async=1000 -f mpegts

The solution I used was to drop the all the "hwaccel" parameters, still
using hw-decoding and encoding. This does impact performance, but it
ensures that if the stream contains material of a different pixel format
that the sws can correct it and transcoding will continue.

I'm not sure if this is a regression in ffmpeg/nvidia or just bad video
material. I hadn't ever run into this until about a month ago. And it's
happened on several videos from different DVD's. I didn't dig into it, I
just dropped the hwaccel parameters and moved on with my life. I wonder if
it's actually a problem in the hw-decoder, but I didn't see any error
messages to prove that.

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