If there isn't other reasons against it, I will suggest to rename the current preset av1.webm to av1_aom.webm This way it inform the users which encoder it is, and also follows the related naming convention av1_svt, av1_vaapi, and possibly additional ffmpeg supported av1_encoders av1-rav1e and avif (image), and additional av1_hwaccels methods (qsv, amf, nvenc) later. And possibly upgrade to svt-av1 v.2.1. Transcoding regarding duration was also mentioned above. My input file here was a cfhd transcoded with ffmpeg from a Prores 422 hq source video file (that is not a arbitrary cut). Alt. 1) Therefore I went back to my source Prores 422 (HQ) hd01.mov which especially default includes 16 channels LPCM audio, even though only 2 ch stereo is used. ffprobe -hide_banner hd01.mov Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'hd01.mov': Metadata: creation_time : 2016-02-23T23:49:21.000000Z Duration: 00:01:11.28, start: 0.000000, bitrate: 200496 kb/s Stream #0:0[0x1](eng): Video: prores (HQ) (apch / 0x68637061), yuv422p10le(bt709, top coded first (swapped)), 1920x1080, 182130 kb/s, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 2500 tbn (default) Metadata: creation_time : 2016-02-23T23:49:21.000000Z handler_name : Apple Video Media Handler vendor_id : appl encoder : Apple ProRes 422 (HQ) Stream #0:1[0x2](eng): Audio: pcm_s24le (lpcm / 0x6D63706C), 48000 Hz, 16 channels, s32 (24 bit), 18432 kb/s (default) Metadata: creation_time : 2016-02-23T23:49:21.000000Z handler_name : Apple Sound Media Handler vendor_id : [0][0][0][0] Loaded this Prores 422 hq source file into CinGG 1) Video only rendering - no error messages Rendering to file /Videoklipp/Cineform/av1_aom_yuv422p10le.webm File format; FFMPEG webm Video only wrench: av1.webm | yuv422p10le cin Cinelerra Infinity - built: Jul 29 2024 01:18:06 .... Render::render_single: Session finished. ** rendered 1781 frames in 187.108 secs, 9.519 fps FFMPEG::open_decoder: some stream times estimated: /run/media/terje/Videoklipp/Cineform/av1_aom_yuv422p10le.webm FFMPEG::open_decoder: some stream times estimated: /run/media/terje/Videoklipp/Cineform/av1_aom_yuv422p10le.webm FFMPEG::open_decoder: some stream times estimated: /run/media/terje/Videoklipp/Cineform/av1_aom_yuv422p10le.webm Total excess of backups: -50 Session time: 0:05:08 Cpu time: user: 0:20:00.969 sys: 0:00:08.355 2) Audio only rendering - not possible in CinGG Cinelerra Infinity - built: Jul 29 2024 01:18:06 - 16 channels lpcm audio (actually only #1 and #2 stereo used) Rendering to file /Videoklipp/Cineform/opus.webm File format; FFMPEG webm Audio only wrench: opus.webm [libopus @ 0x7f637c06a6c0] Opus mapping family undefined for 16 channels. FFMPEG::open_encoder err: Invalid argument int FFMPEG::open_encoder(const char*, const char*): open failed libopus:/run/media/terje/Videoklipp/Cineform/opus.webm Render::render_single: Session finished. Total excess of backups: -50 Session time: 0:02:21 Cpu time: user: 0:00:13.680 sys: 0:00:02.102 ----------------- Alt. 2) Transcoded alt. 1) source input file to Prores 422 hq with 2 ch stereo audio: ffmpeg -hide_banner -i hd01.mov -map_metadata 0 -c:v copy -c:a pcm_s24le -ac 2 hd02.mov ffprobe -hide_banner hd02.mov Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'hd02.mov': Metadata: major_brand : qt minor_version : 512 compatible_brands: qt creation_time : 2016-02-23T23:49:21.000000Z encoder : Lavf61.1.100 Duration: 00:01:11.28, start: 0.000000, bitrate: 184335 kb/s Stream #0:0[0x1](eng): Video: prores (HQ) (apch / 0x68637061), yuv422p10le(bt709, top coded first (swapped)), 1920x1080, 182130 kb/s, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 10k tbn (default) Metadata: creation_time : 2016-02-23T23:49:21.000000Z handler_name : Apple Video Media Handler vendor_id : FFMP encoder : Apple ProRes 422 (HQ) Stream #0:1[0x2](eng): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default) Metadata: creation_time : 2016-02-23T23:49:21.000000Z handler_name : Apple Sound Media Handler vendor_id : [0][0][0][0] ----------------- Alt. 3) Transcoded th source file Prores 422 (HQ) with LPCM audio to CFHD quality 7 (high+), AAC audio (default) to stereo (-ac 2) and Metadata (some) ffmpeg -hide_banner -i hd01.mov -map_metadata 0 -c:v cfhd -quality 7 -ac 2 cfhd01.mov ffprobe -hide_banner cfhd01.mov Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'cfhd01.mov': Metadata: major_brand : qt minor_version : 512 compatible_brands: qt creation_time : 2016-02-23T23:49:21.000000Z encoder : Lavf61.1.100 Duration: 00:01:11.28, start: 0.000000, bitrate: 181871 kb/s Stream #0:0[0x1](eng): Video: cfhd (CFHD / 0x44484643), yuv422p10le(bt709, top coded first (swapped)), 1920x1080, 181846 kb/s, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 12800 tbn (default) Metadata: creation_time : 2016-02-23T23:49:21.000000Z handler_name : Apple Video Media Handler vendor_id : FFMP encoder : Lavc61.3.100 cfhd Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 122 kb/s (default) Metadata: creation_time : 2016-02-23T23:49:21.000000Z handler_name : Apple Sound Media Handler vendor_id : [0][0][0][0] By loading Alt. 2) Prores LPCM or Alt. 3) CFHD AAC with 2 ch stereo audio into CinGG 1) Video only av1_aom.webm rendering caused the previous FFseek I/O errors 2) Audio only hd02.mov stereo lpcm -> opus.webm worked ok cin Cinelerra Infinity - built: Jul 29 2024 01:18:06 ........ Render::render_single: Session finished. ** rendered 1781 frames in 6.387 secs, 278.848 fps FFMPEG::open_decoder: some stream times estimated: /run/media/terje/Videoklipp/Cineform/opus.webm audio0 pad 16 0 (16) FFMPEG::open_decoder: some stream times estimated: /run/media/terje/Videoklipp/Cineform/opus.webm Total excess of backups: -50 Session time: 0:01:49 Cpu time: user: 0:00:15.458 sys: 0:00:02.457