# PNG rendering error troubleshooting (2025-11-01 15:48Z) _**User (2025-11-01 15:48Z)**_ why is this happening to render libpng error: IDAT: CRC error ImageInput::read_image() failed: PNG read error: IDAT: CRC error PNG library error IMB_load_image_from_memory: unknown file-format (R:\Creative\artsy\maya\2025-02 BondingArtifact\Renders\3_background\2025-10-26\3_background_dark\3_background_dark_5489.png) --- _**Assistant (default)**_ --- Reviewing the open file to understand the render configuration and identify why PNGs are being corrupted. --- Tool use: **read_file** Read file: c:\Program Files\Blender Foundation\Flamenco 3.7\scripts\TalkingHeads cycles_optix_gpu_NOBAT.js --- Tool use: **codebase_search**

Searched codebase "How are PNG images saved or written during rendering?" • **3** results

| File | Lines | |------|-------| | `.gitignore` | L134 | | `.gitattributes` | L47 | | `misc/checklist.txt` | L52 |

--- --- Checking the render configuration and the corrupt file path for clues. --- Tool use: **codebase_search**

Searched codebase "Where are render output files written or saved?" • **10** results

| File | Lines | |------|-------| | `.gitignore` | L134 | | `assets/Objects/gems/tx/BlackOnyx/Designer/BlackOnyx.sbs` | L3573-3642 | | `misc/checklist.txt` | L52 | | `misc/metadata.bat` | L23 | | `misc/filenames.bat` | L1 | | `.cursorindexingignore` | L3 | | `.gitattributes` | L47 | | `assets/Objects/gems/tx/BlackOnyx/Designer/BlackOnyx.sbs` | L1475-1533 | | `misc/BRANDING.txt` | L2 | | `assets/Objects/gems/tx/BlackOnyx/Designer/BlackOnyx.sbs` | L1976-2034 |

--- Tool use: **grep**

Grep for "3_background" • 0 matches

Output mode: content _No matches found_

--- --- This PNG CRC error indicates the file was corrupted during render. The path `R:\...` suggests a network drive, which is a common source. Common causes: - Network storage issues: timeouts, interruptions, or bad connections corrupt writes - Concurrent access: another process (comp, preview, antivirus) reading while a worker writes - Incomplete writes: file read before the write finishes - Antivirus/backup: scanning or copying files while they’re being written Checking the render script for timing or synchronization issues: --- Tool use: **read_file** Read file: c:\Program Files\Blender Foundation\Flamenco 3.7\scripts\TalkingHeads cycles_optix_gpu_NOBAT.js --- --- ## Solutions to fix this: ### **Immediate fixes:** 1. **Check if the file is actually corrupted** - Verify frame `5489` on the R: drive - If corrupted, re-render just that frame 2. **Render to local storage first, then copy** - Change the render output to a local drive (C: or D:) - After rendering completes, copy to the network drive - Reduces corruption risk from network interruptions 3. **Increase chunk_size** - In your Flamenco job settings, increase `chunk_size` (currently defaults to 1) - Fewer concurrent writes = less contention 4. **Temporarily disable antivirus/backup scanning** - Exclude the render output folder from real-time scanning - Network drives are often scanned aggressively ### **Network storage specific:** 5. **Check network drive health** - Test the R: drive connection stability - Run `chkdsk R: /f` if it's accessible - Check for network timeouts or packet loss 6. **Add file write delay/sync** - If possible, configure Blender to flush writes completely before finishing - Use `--python-expr` to add a small delay after rendering completes ### **For the current corrupted frame:** The file `3_background_dark_5489.png` is corrupted. Either: - Re-render frame 5489 specifically, or - Skip it and continue (if it's not critical) Should I help modify the Flamenco script to render to a local directory first, or focus on diagnosing the network storage issue? ---