File size: 2,164 Bytes
6461f0c | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 | """Uniform frame sampling from a video into base64-encoded JPEG strings."""
from __future__ import annotations
import base64
import io
import os
import cv2
from PIL import Image
DEFAULT_NUM_SAMPLE_FRAMES: int = 8
def extract_frames_from_video(
video_path: str,
num_frames: int = DEFAULT_NUM_SAMPLE_FRAMES,
jpeg_quality: int = 90,
verbose: bool = True,
) -> list[str]:
"""Uniformly sample frames from a video and return them as base64 JPEGs.
Returns
-------
list[str]
Base64-encoded JPEG strings, in temporal order
(frame 1 = earliest, frame N = latest).
"""
cap = cv2.VideoCapture(video_path)
if not cap.isOpened():
raise RuntimeError(f"Cannot open video: {video_path}")
fps = cap.get(cv2.CAP_PROP_FPS)
total_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
if fps <= 0 or total_frames <= 0:
cap.release()
raise RuntimeError(
f"Invalid video metadata: fps={fps}, total_frames={total_frames}"
)
duration = total_frames / fps
num_to_sample = max(1, min(int(num_frames), total_frames))
if num_to_sample == 1:
sample_indices = [0]
else:
sample_indices = [
int(round(i * (total_frames - 1) / (num_to_sample - 1)))
for i in range(num_to_sample)
]
frame_b64_list: list[str] = []
for frame_idx in sample_indices:
cap.set(cv2.CAP_PROP_POS_FRAMES, frame_idx)
ret, frame = cap.read()
if not ret:
continue
frame_rgb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
img = Image.fromarray(frame_rgb)
buf = io.BytesIO()
img.save(buf, format="JPEG", quality=int(jpeg_quality))
frame_b64_list.append(base64.b64encode(buf.getvalue()).decode("utf-8"))
cap.release()
if not frame_b64_list:
raise RuntimeError(f"Failed to extract any frames from {video_path}")
if verbose:
print(
f" [frames] Extracted {len(frame_b64_list)} frames from "
f"{os.path.basename(video_path)} "
f"(duration={duration:.1f}s, fps={fps:.1f})"
)
return frame_b64_list
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