Avidemux Forum

Quote from: Rainman74 on Today at 12:43:03 PMWith the current nightly build, the error message no longer appears; instead, the app crashes and freezes.

This is https://avidemux.org/smif/index.php?msg=98711, related to the libavcodec-based AC3 encoder. NVENC-based video encoders are working for you now, aren't they?

Quote from: eumagga0x2a on October 09, 2026, 06:25:32 AMPlease try the 20261009 nightly from https://avidemux.org/nightly/win64/ without this workaround (i.e. with AVX and AVX2 enabled) and report back whether the tentative fix resolves the issue for you, thanks.

I retract my request, for some unclear reason libavcodec AC3 encoder in my local build didn't crash with that patch a few times in a row. The "fix" hasn't solved the issue, unfortunately. Therefore disabling AVX and AVX2 is still required.

Quote from: eumagga0x2a on October 02, 2026, 06:24:54 PM

Quote from: Rainman74 on October 02, 2026, 09:04:45 AMSince avidemux_mingw64_20260912 & 20260922, the nvenc encoders no longer work and throw an error.

May be related to graphics drivers being too old, in doubt please reproduce the issue, close Avidemux and provide admlog.txt from %localappdata%\avidemux directory.

With the current nightly build, the error message no longer appears; instead, the app crashes and freezes.

Here are all the logs: https://pixeldrain.com/u/HbLohN4k

Addendum: Specific requirements for archiving analog tape sources (Hi8, S-VHS / Video8, VHS)

To provide further context and technical justification, these requests stem from real-world CLI encoding tests (ffmpeg with libx265) on digitized analog tape media. Analog sources present unique encoding challenges due to tape noise, time-base instability, and chroma bleeding.

To achieve optimal preservation without resorting to external CLI scripts, the following GUI parameters are also needed:

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4. Floating-point CRF values (0.1 / 0.5 precision steps)

• Current limitation: The GUI only accepts integer CRF values.

• The issue with analog video: Due to high entropy from analog noise, moving from CRF 18 to 19 causes a massive drop in bitrate and detail. A integer-only scale is too coarse.

• Proposed fix: Change the CRF input field from an integer control to a decimal input (QDoubleSpinBox), allowing values like 18.5 or 19.2. libx265 natively processes double-precision CRF values.

• Corresponding FFmpeg / x265 CLI parameters:
-x265-params crf=18.5 (or -crf 18.5)
5. Chroma QP Offsets (cbqpoffs / crqpoffs) & qcomp

• Current limitation: Not configurable in the Avidemux GUI.

• The issue with analog video: Analog chroma channels contain heavy noise. Being able to fine-tune cbqpoffs and crqpoffs prevents the encoder from wasting bitrate on color bleeding/noise while preserving luminance structure.

• Corresponding FFmpeg / x265 CLI parameters:
-x265-params cbqpoffs=-1:crqpoffs=-1:qcomp=0.60
6. SAO Non-Deblock Handling (`--sao-non-deblock`)

• Current limitation: Completely missing from the Avidemux GUI.

• The issue with analog video: Default SAO interaction with deblocking creates severe haloing and strips away natural tape grain. Being able to explicitly set `sao-non-deblock` prevents smudging fine details on tape captures.

• Corresponding FFmpeg / x265 CLI parameters:
-x265-params sao-non-deblock=1

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NB: Tests using native ffmpeg parameters prove that having access to these specific float values and sub-parameters makes a night-and-day difference in visual fidelity for digitized analog media.

Best regards,

Manfred

Quote from: jimmy on October 02, 2026, 10:44:55 PMGoing forward, should AVX and AVX2 be kept disabled, or is that just for a temporary fix?

Disabling AVX and AVX2 is a workaround, not a fix of any kind. Please try the 20261009 nightly from https://avidemux.org/nightly/win64/ without this workaround (i.e. with AVX and AVX2 enabled) and report back whether the tentative fix resolves the issue for you, thanks.

[Feature Request] Add fine-grained x265 GUI controls for --deblock, --sao, and --sao-non-deblock

Hi team,

I would like to request an enhancement for the x265 video encoder GUI in Avidemux regarding the Deblock and SAO (Sample Adaptive Offset) settings.

Currently, the GUI only provides basic toggle options (checkboxes) to disable these filters, but lacks fine-tuning parameters that are crucial for specific encoding scenarios (such as capturing interlaced analog video sources, tape digitizations, or lower-bitrate DVB streams).

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Missing / Limited Settings:

1. Deblock Filter (--deblock)

• Current state: Only available as a binary toggle/checkbox (Disable Deblock).

• Requested feature: Expose the two offset parameters Alpha (tcOffset) and Beta (betaOffset).

• Corresponding FFmpeg / x265 CLI parameters:
-x265-params deblock=<cbOffset>:<crOffset> (e.g. -x265-params deblock=-1:-1)
2. Sample Adaptive Offset (--sao)   

• Current state: Only available as a binary toggle/checkbox (Disable SAO).

• Requested feature: Allow further customization of SAO behavior (e.g. mode selection, limit-sao, or custom thresholds) instead of just a global ON/OFF switch.

• Corresponding FFmpeg / x265 CLI parameters:
-x265-params sao=1 / sao=0 and -x265-params limit-sao=1
3. SAO Non-Deblock Handling (--sao-non-deblock)   

• Current state: Missing completely from the GUI.

• Requested feature: Add a toggle/setting to specify how SAO handles dependency on deblocked edge pixels.

• Corresponding FFmpeg / x265 CLI parameters:   
-x265-params sao-non-deblock=1 / sao-non-deblock=0

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Exposing numerical inputs and toggles for these settings in the x265 plugin configuration (and storing them in the plugin JSON config) would give users precise control over fine details and prevent blurring/banding artifacts without relying on external scripts or CLI runs.

Thank you very much for considering this improvement!
And also thanks a lot for your continuous hard work on Avidemux and for keeping this awesome tool alive over all these years!

Best regards,
Manfred

Thank-you.

Just for my own satisfaction, I reproduced the freeze-up on the first try.

Quote from: eumagga0x2a on October 02, 2026, 08:13:17 PMPlease disable AVX and AVX2 SIMD in Avidemux Preferences --> CPU and report back whether this helps.

This worked, Sep 22 nightly did not freeze-up.

Going forward, should AVX and AVX2 be kept disabled, or is that just for a temporary fix?

Please disable AVX and AVX2 SIMD in Avidemux Preferences --> CPU and report back whether this helps.

I have seen this intermittent FFmpeg crash encoding audio to AC3 too, thank you for the log. Not related to x264 or anything else.

Quote from: Rainman74 on October 02, 2026, 09:04:45 AMSince avidemux_mingw64_20260912 & 20260922, the nvenc encoders no longer work and throw an error.

May be related to graphics drivers being too old, in doubt please reproduce the issue, close Avidemux and provide admlog.txt from %localappdata%\avidemux directory.