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[BUG] QTGMC deinterlaced video has audio desynchronisation - Printable Version

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QTGMC deinterlaced video has audio desynchronisation - chris - 22.12.2025

Hi Selur and everyone else,

I'm using Hybrid 2025.11.09.1 installed on my new PC.

I've noticed when I attempting to process interlaced captures, output files have a synchronisation issue - it's more of a constant offset rather than a drift.


Here's an example input file, a 720x576 interlaced 25 fps video in HuffYUV and PCM. I am attempting to encode using either x264 or x265 and AAC FDK audio, bob deinterlacing using QTGMC and scaling to 768x576 (standard adjustment for PAL SD non-square footage). 

I made these captures myself using AmaRecTV on my Avermedia C027 card from a professional Panasonic SVHS deck. I've used AmaRecTV and the capture device for many years and I trust that it's capturing and encoding everything in sync.

The AVI plays in sync in MPC-HC, mpv or VLC. If I remux the .avi with MKVToolNix, it also plays in sync in those programs.

ffprobe -v error -show_format -show_streams otuput:

[STREAM] index=0 codec_name=huffyuv codec_long_name=HuffYUV profile=unknown codec_type=video codec_tag_string=HFYU codec_tag=0x55594648 width=720 height=576 coded_width=720 coded_height=576 closed_captions=0 film_grain=0 has_b_frames=0 sample_aspect_ratio=N/A display_aspect_ratio=N/A pix_fmt=yuv422p level=-99 color_range=unknown color_space=unknown color_transfer=unknown color_primaries=unknown chroma_location=unspecified field_order=unknown refs=1 id=N/A r_frame_rate=25/1 avg_frame_rate=25/1 time_base=1/25 start_pts=0 start_time=0.000000 duration_ts=11203 duration=448.120000 bit_rate=78324880 max_bit_rate=N/A bits_per_raw_sample=N/A nb_frames=11203 nb_read_frames=N/A nb_read_packets=N/A extradata_size=192 DISPOSITION:default=0 DISPOSITION:dub=0 DISPOSITION:original=0 DISPOSITION:comment=0 DISPOSITION:lyrics=0 DISPOSITION:karaoke=0 DISPOSITION:forced=0 DISPOSITION:hearing_impaired=0 DISPOSITION:visual_impaired=0 DISPOSITION:clean_effects=0 DISPOSITION:attached_pic=0 DISPOSITION:timed_thumbnails=0 DISPOSITION:non_diegetic=0 DISPOSITION:captions=0 DISPOSITION:descriptions=0 DISPOSITION:metadata=0 DISPOSITION:dependent=0 DISPOSITION:still_image=0 [/STREAM] [STREAM] index=1 codec_name=pcm_s16le codec_long_name=PCM signed 16-bit little-endian profile=unknown codec_type=audio codec_tag_string=[1][0][0][0] codec_tag=0x0001 sample_fmt=s16 sample_rate=48000 channels=2 channel_layout=unknown bits_per_sample=16 initial_padding=0 id=N/A r_frame_rate=0/0 avg_frame_rate=0/0 time_base=1/48000 start_pts=0 start_time=0.000000 duration_ts=N/A duration=N/A bit_rate=1536000 max_bit_rate=N/A bits_per_raw_sample=N/A nb_frames=21509760 nb_read_frames=N/A nb_read_packets=N/A DISPOSITION:default=0 DISPOSITION:dub=0 DISPOSITION:original=0 DISPOSITION:comment=0 DISPOSITION:lyrics=0 DISPOSITION:karaoke=0 DISPOSITION:forced=0 DISPOSITION:hearing_impaired=0 DISPOSITION:visual_impaired=0 DISPOSITION:clean_effects=0 DISPOSITION:attached_pic=0 DISPOSITION:timed_thumbnails=0 DISPOSITION:non_diegetic=0 DISPOSITION:captions=0 DISPOSITION:descriptions=0 DISPOSITION:metadata=0 DISPOSITION:dependent=0 DISPOSITION:still_image=0 [/STREAM] [FORMAT] filename=amarec(20251120-2051).avi nb_streams=2 nb_programs=0 format_name=avi format_long_name=AVI (Audio Video Interleaved) start_time=0.000000 duration=448.120000 size=4473288704 bit_rate=79858764 probe_score=100 [/FORMAT]



I have found if I manually offset the audio to around -800 ms then the audio is more synchronised. I've tried Vapoursynth and Avisynth in the Filtering tab.

Here's a MediaInfo output of the source file:

General Complete name                            : D:\caps\amarectv231_en\amarec(20251120-2051).avi Format                                  : AVI Format/Info                              : Audio Video Interleave Format settings                          : WaveFormatEx File size                                : 4.17 GiB Duration                                : 7 min 28 s Overall bit rate                        : 79.9 Mb/s Frame rate                              : 25.000 FPS Video ID                                      : 0 Format                                  : HuffYUV Format version                          : Version 2 Codec ID                                : HFYU Duration                                : 7 min 28 s Bit rate                                : 75.2 Mb/s Width                                    : 720 pixels Height                                  : 576 pixels Display aspect ratio                    : 5:4 Frame rate                              : 25.000 FPS Standard                                : PAL Color space                              : YUV Chroma subsampling                      : 4:2:2 Bit depth                                : 8 bits Scan type                                : Interlaced Bits/(Pixel*Frame)                      : 7.248 Stream size                              : 3.92 GiB (94%) Audio ID                                      : 1 Format                                  : PCM Format settings                          : Little / Signed Codec ID                                : 1 Duration                                : 7 min 28 s Bit rate mode                            : Constant Bit rate                                : 1 536 kb/s Channel(s)                              : 2 channels Sampling rate                            : 48.0 kHz Bit depth                                : 16 bits Stream size                              : 82.1 MiB (2%) Alignment                                : Aligned on interleaves ReportBy                                : MediaInfoLib - v24.12 CreatedOn                                : UTC 2025-12-22 16:12:38



Not sure what other info you'd like? I can clip a short section of this file and supply as .avi or .mkv if it would help, though I'm not sure what else I can do to try and stop this A/V sync issue.

I also noticed a couple of other things:

* Hybrid is incorrectly detecting the interlacing as BFF when the file is TFF interlaced, even when it runs its own evaluative scan. Is Hybrid incorrectly assuming it's a DV clip based on resolution and PAR?
* When Vapoursynth is loaded, it claims "Detected no AVX2 support", although this CPU (AMD R9 7950X) supports AVX, AVX2 & AVX512.

Cheers!
Chris

RE: QTGMC deinterlaced video has audio desynchronisation - Bartoloni - 22.12.2025

usually related to use MP4 as output (changing to MKV can solve)
with MP4.. using FFMPEG instead of MP4BOX can solve also.

P.S. you don't need to "SCALE"... just leave 720x576... and force an INPUT PAR 16:15 ( for 4/3 PAL ) and leave "resizing" to the player.

RE: QTGMC deinterlaced video has audio desynchronisation - Selur - 22.12.2025

Quote:* Hybrid is incorrectly detecting the interlacing as BFF when the file is TFF interlaced, even when it runs its own evaluative scan.
a. source is only flagged as interlaced not as tff or bff, so there is no way to know from the flags
b. the heuristic might be guessing to depending on the results
Quote:Is Hybrid incorrectly assuming it's a DV clip based on resolution and PAR?
I do not think so.
Quote:When Vapoursynth is loaded, it claims "Detected no AVX2 support", although this CPU (AMD R9 7950X) supports AVX, AVX2 & AVX512.
Strange, I got the same CPU here and that does not happen here. Huh

About the sync issue:
Might be:
a. because of the source filter used
b. because of an issue with the source
1. try whether telling Hybrid to decode to cfr helps.
2. try whether remuxing to mkv before feeding the file to Hybrid helps.

Cu Selur

Ps.: read the sticky and share a debug output if you need further help