VESPER / code /evaluation /_api.py
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# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: LicenseRef-NVIDIA-OneWay-Noncommercial
"""OpenAI-compatible chat-completions client for the evaluated models and the judge.
A clip is sent in one of two ways:
* ``gemini_video``: the whole clip as one ``image_url`` part holding a
``data:video/mp4;base64,...`` URL.
* ``openai_frames``: JPEG frames spread evenly across the clip, one
``image_url`` part each.
"""
from __future__ import annotations
import base64
import importlib.util
import json
import os
import socket
import sys
import time
import urllib.error
import urllib.request
CHAT_COMPLETIONS_URL = (os.environ.get("VLM_API_BASE", "").rstrip("/") + "/v1/chat/completions") if os.environ.get("VLM_API_BASE", "") else ""
# HTTP statuses worth retrying: server errors, gateway failures and rate limits.
# A failed request is dropped from the run, so transient errors must be retried.
RETRYABLE_STATUS = frozenset({429, 500, 502, 503, 504})
# Socket timeout for every chat-completions POST. Without one, urlopen can block
# forever on a dead connection.
HTTP_TIMEOUT_SEC = float(os.environ.get("VLM_HTTP_TIMEOUT_SEC", "600"))
# Attempts per request to an evaluated model (retryable errors only), and the
# wait between attempts.
API_MAX_ATTEMPTS = 10
API_RETRY_WAIT_SEC = 5
def post_chat_completion(
url: str,
api_key: str,
payload: dict,
server_error_max_attempts: int,
server_error_wait_sec: int,
) -> dict:
headers = {
"Authorization": f"Bearer {api_key}",
"Content-Type": "application/json",
}
data = json.dumps(payload).encode("utf-8")
attempts = max(1, server_error_max_attempts)
for attempt in range(1, attempts + 1):
req = urllib.request.Request(url, data=data, headers=headers, method="POST")
body = ""
try:
with urllib.request.urlopen(req, timeout=HTTP_TIMEOUT_SEC) as resp:
if resp.status < 200 or resp.status >= 300:
print(f"Request failed with HTTP {resp.status}: {url}", file=sys.stderr)
sys.exit(1)
body = resp.read().decode("utf-8")
except urllib.error.HTTPError as e:
err_body = e.read().decode("utf-8", errors="replace")
if e.code in RETRYABLE_STATUS and attempt < attempts:
print(
f"HTTP {e.code} on POST {url} "
f"(attempt {attempt}/{attempts}), retrying in {server_error_wait_sec}s...",
file=sys.stderr,
)
time.sleep(server_error_wait_sec)
continue
print(f"Request failed with HTTP {e.code}: {url}", file=sys.stderr)
if err_body:
print(err_body[:2000], file=sys.stderr)
sys.exit(1)
except (TimeoutError, socket.timeout, urllib.error.URLError) as e:
# MUST stay below the HTTPError clause: HTTPError subclasses URLError,
# so ordering it first would swallow every HTTP status here.
# A stalled connection is retried exactly like a 5xx.
if attempt < attempts:
print(
f"{type(e).__name__} on POST {url} "
f"(attempt {attempt}/{attempts}), retrying in {server_error_wait_sec}s...",
file=sys.stderr,
)
time.sleep(server_error_wait_sec)
continue
print(
f"Request failed after {attempts} attempts ({type(e).__name__}): {url}",
file=sys.stderr,
)
sys.exit(1)
if not body:
return {}
return json.loads(body)
sys.exit(1)
def video_mime_from_path(path: str) -> str:
lower = path.lower()
if lower.endswith(".mp4"):
return "video/mp4"
if lower.endswith(".webm"):
return "video/webm"
if lower.endswith(".mov"):
return "video/quicktime"
if lower.endswith(".mpeg") or lower.endswith(".mpg"):
return "video/mpeg"
print(
"Unsupported video extension (use .mp4, .webm, .mov, .mpeg, .mpg): "
f"{path}",
file=sys.stderr,
)
sys.exit(1)
def video_data_uri_from_file(video_path: str) -> str:
p = video_path if os.path.isabs(video_path) else os.path.abspath(video_path)
if not os.path.isfile(p):
print(f"Video file not found: {p}", file=sys.stderr)
sys.exit(1)
with open(p, "rb") as f:
raw = f.read()
if not raw:
print(f"Video file is empty: {p}", file=sys.stderr)
sys.exit(1)
b64 = base64.standard_b64encode(raw).decode("ascii")
return f"data:{video_mime_from_path(p)};base64,{b64}"
def build_messages_gemini_video(question: str, video_data_uri: str) -> list[dict]:
"""Question text plus one image_url part holding the whole clip."""
return [
{
"role": "user",
"content": [
{"type": "text", "text": question},
{
"type": "image_url",
"image_url": {"url": video_data_uri},
},
],
}
]
def load_cv2():
if importlib.util.find_spec("cv2") is None:
print(
"Frame mode needs OpenCV: pip install opencv-python-headless",
file=sys.stderr,
)
sys.exit(1)
import cv2
return cv2
def extract_jpeg_base64_frames(video_path: str, max_frames: int) -> list[str]:
"""Return up to ``max_frames`` JPEG frames spread evenly from the first to the last frame."""
cv2 = load_cv2()
cap = cv2.VideoCapture(video_path)
if not cap.isOpened():
print(f"Cannot open video for frame extraction: {video_path}", file=sys.stderr)
sys.exit(1)
total = int(cap.get(cv2.CAP_PROP_FRAME_COUNT) or 0)
out: list[str] = []
if total <= 0:
# Frame count unavailable: decode everything, then subsample evenly.
frames = []
while True:
ok, fr = cap.read()
if not ok:
break
frames.append(fr)
cap.release()
if not frames:
return out
n = min(max_frames, len(frames))
idxs = [round(i * (len(frames) - 1) / max(1, n - 1)) for i in range(n)] if n > 1 else [0]
for i in idxs:
ok, buf = cv2.imencode(".jpg", frames[i])
if ok:
out.append(base64.standard_b64encode(buf.tobytes()).decode("ascii"))
return out
n = min(max_frames, total)
idxs = [round(i * (total - 1) / max(1, n - 1)) for i in range(n)] if n > 1 else [0]
for i in idxs:
cap.set(cv2.CAP_PROP_POS_FRAMES, i)
ok, fr = cap.read()
if not ok:
continue
enc_ok, buf = cv2.imencode(".jpg", fr)
if enc_ok:
out.append(base64.standard_b64encode(buf.tobytes()).decode("ascii"))
cap.release()
return out
def build_messages_openai_frames(question: str, jpeg_base64_frames: list[str]) -> list[dict]:
"""Question text plus one data:image/jpeg;base64,... part per frame."""
parts: list[dict] = [{"type": "text", "text": question}]
for b64 in jpeg_base64_frames:
parts.append(
{
"type": "image_url",
"image_url": {"url": f"data:image/jpeg;base64,{b64}"},
}
)
return [{"role": "user", "content": parts}]
def resolve_input_mode(flag: str, model: str) -> str:
"""``auto`` sends frames to GPT models and the whole clip to every other model."""
if flag in ("openai_frames", "gemini_video"):
return flag
m = (model or "").lower()
if "gpt-" in m or "/gpt" in m:
return "openai_frames"
return "gemini_video"
def extract_assistant_text(response: dict) -> str:
choices = response.get("choices")
if not isinstance(choices, list) or not choices:
return ""
ch0 = choices[0]
if not isinstance(ch0, dict):
return ""
msg = ch0.get("message")
if not isinstance(msg, dict):
return ""
content = msg.get("content")
if isinstance(content, str):
return content.strip()
if isinstance(content, list):
parts: list[str] = []
for part in content:
if not isinstance(part, dict):
continue
if part.get("type") == "text":
t = (part.get("text") or "").strip()
if t:
parts.append(t)
return "\n".join(parts).strip()
return ""
def query_model(
video_path: str,
question: str,
model: str,
api_url: str,
api_key: str,
input_mode: str,
max_frames: int,
robot_type: str = "",
) -> str:
"""Send the clip and question to a model and return its answer text."""
if resolve_input_mode(input_mode, model) == "openai_frames":
messages = build_messages_openai_frames(
question, extract_jpeg_base64_frames(video_path, max_frames),
)
else:
messages = build_messages_gemini_video(question, video_data_uri_from_file(video_path))
if robot_type:
messages = [
{"role": "system", "content": f"You are a {robot_type}."},
*messages,
]
payload = {"model": model, "messages": messages}
response = post_chat_completion(
api_url, api_key, payload, API_MAX_ATTEMPTS, API_RETRY_WAIT_SEC,
)
return extract_assistant_text(response)