VAAPI transcoding fails most of the time

[mrdally204]

Hey all,

I'm having an intermittent transcoding issue with NextPVR on Ubuntu 24.04 using VAAPI hardware acceleration. Most transcoding attempts fail, but occasionally they work without any changes.

Intel® Core™ i5-7500T CPU
Driver version: Intel iHD driver for Intel® Gen Graphics - 24.1.0 ()

I've verified permissions on /dev/dri/renderD128, the nextpvr user is in the video and render groups, and vainfo reports VAAPI support.
I've attached my latest logs (zip), which include both successful and failed transcoding attempts.
Any ideas on what I should check next?

[mvallevand]

According to AI it is an FFMpeg bug with vaapi and closed captioning

2026-07-13 23:06:33.841 [DEBUG][10] [FFMPEG]: [h264_vaapi @ 0x573065a76900] Access unit too large: 8192 < 10752.

Maybe try this in config.xml instead of the default <TranscodeHLS>default</TranscodeHLS> (I didn't test it)

Code:

-hwaccel vaapi -hwaccel_output_format vaapi  -y [ANALYZE_DURATION] [SEEK] -vaapi_device /dev/dri/renderD128 -i [SOURCE] -map_metadata -1 -threads 0 -ignore_unknown -map 0:v:0? -map 0:a:[AUDIO_STREAM] -map -0:s -vf "scale_vaapi=[VAAPI_SCALE]" -codec:v:0 h264_vaapi -sei 0 -max_muxing_queue_size 2048 -b:v [BITRATE] -maxrate [BITRATE] -bufsize [BUFSIZE] -codec:a:0 [AUDIO_CODEC] -strict experimental -ac [AUDIO_CHANNELS] -ab [AUDIO_BITRATE] -hls_time [SEGMENT_DURATION] -start_number 0 -hls_list_size [SEGMENT_COUNT] -y [TARGET]

If not work with AI to come up with parameters if you absolutely must use VAAPI or just move to a direct play client.

Martin

[mrdally204]

According to AI it is an FFMpeg bug with vaapi and closed captioning

2026-07-13 23:06:33.841 [DEBUG][10] [FFMPEG]: [h264_vaapi @ 0x573065a76900] Access unit too large: 8192 < 10752.

Maybe try this in config.xml  instead of the default <TranscodeHLS>default</TranscodeHLS> (I didn't test it)

Code:

-hwaccel vaapi -hwaccel_output_format vaapi  -y [ANALYZE_DURATION] [SEEK] -vaapi_device /dev/dri/renderD128 -i [SOURCE] -map_metadata -1 -threads 0 -ignore_unknown -map 0:v:0? -map 0:a:[AUDIO_STREAM] -map -0:s -vf "scale_vaapi=[VAAPI_SCALE]" -codec:v:0 h264_vaapi -sei 0 -max_muxing_queue_size 2048 -b:v [BITRATE] -maxrate [BITRATE] -bufsize [BUFSIZE] -codec:a:0 [AUDIO_CODEC] -strict experimental -ac [AUDIO_CHANNELS] -ab [AUDIO_BITRATE] -hls_time [SEGMENT_DURATION] -start_number 0 -hls_list_size [SEGMENT_COUNT] -y [TARGET]

If not work with AI to come up with parameters if you absolutely must use VAAPI or just move to a direct play client.

Martin

Thanks for the response, Martin. If I make changes to the config.xml will they persist with future NextPVR updates?

[mvallevand]

Yes. However default might change internally and improve on your settings.

Martin

[mrdally204]

Yes.  However default might change internally and improve on your settings.

Martin

Confirmed. The changes you suggested above to the config fixed the transcoding problem I was experiencing. Thanks again!