invoke-ai/InvokeAI · error · ValueError

Cannot determine frame count for {self.video.video_name}: pr

Error message

Cannot determine frame count for {self.video.video_name}: probe returned duration={duration}, fps={source_fps}.

What it means

Thrown in VideoFrameExtractRange.invoke when the total frame count is needed but cannot be determined: decoder_frame_count returned None and the probe fallback has invalid fps or non-positive duration. A range extraction requires knowing how many frames exist to resolve start/end indices.

Source

Thrown at invokeai/app/invocations/video_frame_extract_range.py:150

        description=("Last frame to keep, inclusive. -1 = last frame. Negative indices count from the end."),
        ui_component=UIComponent.VideoFrameIndex,
    )
    fps: int = InputField(
        default=0,
        ge=0,
        le=120,
        description="Output frame rate. 0 = match the source video's frame rate "
        "(falls back to 16 fps if the source rate can't be probed).",
    )

    def invoke(self, context: InvocationContext) -> ExtractVideoRangeOutput:
        video_path = context.videos.get_path(self.video.video_name)
        width, height, duration, source_fps = probe_video(video_path)

        n_frames = decoder_frame_count(video_path)
        if n_frames is None:
            if not source_fps or duration <= 0:
                raise ValueError(
                    f"Cannot determine frame count for {self.video.video_name}: "
                    f"probe returned duration={duration}, fps={source_fps}."
                )
            n_frames = int(round(duration * source_fps))
        if n_frames <= 0:
            raise ValueError(f"Video {self.video.video_name} has no decodable frames (probed {n_frames}).")

        start = self._resolve_index(self.start_frame, n_frames, "start_frame")
        end = self._resolve_index(self.end_frame, n_frames, "end_frame")
        if end < start:
            raise ValueError(
                f"end_frame ({self.end_frame} → {end}) must be >= start_frame "
                f"({self.start_frame} → {start}) after resolving negative indices."
            )

        # Derive the output frame rate from the source video when ``fps`` is 0
        # (the default), so a trimmed clip plays back at the same speed as its
        # source. Fall back to 16 fps (the Wan video default) when the source

View on GitHub (pinned to 0b6a024f2f)

Solutions

  1. Re-encode to a standard MP4/H.264 so both duration and fps are readable
  2. Use ffprobe to verify the file reports valid duration and fps
  3. Provide a complete, finalized source file (finalize camera recordings)
  4. Extract frames by time range from a working source instead

Example fix

// before
# fragmented.mp4 has no duration metadata
VideoFrameExtractRange(video=frag, start_frame=0, end_frame=-1)
// after
ffmpeg -i fragmented.mp4 -c copy repaired.mp4
VideoFrameExtractRange(video=repaired, start_frame=0, end_frame=-1)
Defensive patterns

Strategy: fallback

Validate before calling

probe = probe_video(path)
if decoder_frame_count(path) is None and (not probe.fps or probe.duration <= 0):
    raise ValueError(f'{path}: frame count undeterminable; re-encode first')

Type guard

def has_known_length(probe) -> bool:
    return bool(probe.fps) and probe.duration > 0

Try / catch

try:
    out = range_extract.invoke(context)
except ValueError as e:
    if 'Cannot determine frame count' in str(e):
        run_ffmpeg(['-i', path, '-c', 'copy', repaired_path])
        out = rebuild(video=repaired_path).invoke(context)
    else:
        raise

Prevention

When it happens

Trigger: invoke(): decoder_frame_count(video_path) is None and probe_video returns source_fps falsy or duration <= 0.

Common situations: Corrupt containers without duration metadata; fragmented/unfinalized recordings; streams without fps info.

Related errors

AI-assisted analysis of invoke-ai/InvokeAI@0b6a024f2f (2026-08-29). Data as JSON: /api/errors/d6fa4cb19b8da7df. Report an issue: GitHub.