from video_reader import PyVideoReader

vr = PyVideoReader(filename)
# or if you want to resize and use a specific number of threads
vr = PyVideoReader(filename, threads=8, resize_shorter_side=480)
# similar but by resizing longer side
vr = PyVideoReader(filename, threads=8, resize_longer_side=640)
# or to use GPU decoding:
vr = PyVideoReader(filename, device='cuda')

# decode all frames from the video
frames = vr.decode()
# or decode a subset of frames
frames = vr.decode(start_frame=100, end_frame=300, compression_factor=0.5)
# alternatively one can iterate over frames
for frame in vr:
    # do something with a single frame
    print("top left red pixel value:", frame[0, 0, 0])

# this method has the same arguments as decode()
frames = vr.decode_gray()

frames = vr.get_batch(indices)

# Default: raise error on out-of-bounds
vr = PyVideoReader(filename)

# Skip mode: skip invalid frames, returned array may be smaller
vr = PyVideoReader(filename, oob_mode="skip")
frames = vr.get_batch([0, 1, 999999])  # Returns 2 frames if 999999 is invalid

# Black mode: return black (all-zero) frames for invalid indices
vr = PyVideoReader(filename, oob_mode="black")
frames = vr.get_batch([0, 1, 999999])  # Returns 3 frames, last one is all zeros

last_frame = vr[-1]
odd_frames = vr[1::2]
sub_clip = vr[128:337]

# (number of frames, height, width)
(n, h, w) = vr.get_shape()
# if we only want the number of frames
n = len(vr)

info_dict = vr.get_info()
print(info_dict)
# example output:
# {'color_space': 'BT709', 'aspect_ratio': 'Rational(1/1)', 'color_xfer_charac': 'BT709', 'codec_id': 'H264', 'fps_rational': '0/1', 'width': '1280', 'vid_ref': '1', 'duration': '148.28736979166666', 'height': '720', 'has_b_frames': 'true', 'color_primaries': 'BT709', 'chroma_location': 'Left', 'time_base': '0.00006510416666666667', 'vid_format': 'YUV420P', 'bit_rate': '900436', 'fps': '33.57669643068823', 'start_time': '0', 'color_range': 'MPEG', 'intra_dc_precision': '0', 'frame_count': '4979'}

from video_reader import PyVideoReader

videoname = "/path/to/your/video.mp4"
vr = PyVideoReader(videoname)

chunk_size = 800 # adjust to fit within your memory limit
video_length = vr.get_shape()[0]

for i in range(0, video_length, chunk_size):
    end = min(i + chunk_size, video_length)
    frames = vr.decode_fast(
        start_frame=i,
        end_frame=end,
    )
    # do something with this chunk of 800 `frames`

from video_reader import PyVideoReader

# Scale to fixed 256x256 (no aspect ratio preservation)
vr = PyVideoReader(
    filename,
    filter="format=yuv420p,scale=w=256:h=256:flags=fast_bilinear"
)

# Use higher quality scaling
vr = PyVideoReader(
    filename,
    filter="format=yuv420p,scale=w=224:h=224:flags=lanczos"
)

# ❌ Wrong - may crash on some videos
filter="scale=w=256:h=256"

# ✅ Correct - works with all videos
filter="format=yuv420p,scale=w=256:h=256"

filter="format=yuv420p,scale=256:256"  # width:height

# Crop center 480x480 then scale to 256x256
filter="format=yuv420p,crop=w=480:h=480,scale=w=256:h=256:flags=lanczos"

# Scale width to 256, height auto (preserve aspect ratio)
filter="format=yuv420p,scale=w=256:h=-1:flags=bilinear"

# Scale height to 256, width auto (preserve aspect ratio)  
filter="format=yuv420p,scale=w=-1:h=256:flags=bilinear"

# Pad to square before scaling (letterbox)
filter="format=yuv420p,pad=w=max(iw\,ih):h=max(iw\,ih):x=(ow-iw)/2:y=(oh-ih)/2,scale=w=256:h=256"

# ❌ Error: Multiple resize methods
vr = PyVideoReader(path, target_width=224, target_height=224, resize_shorter_side=256)

# ❌ Error: Multiple resize methods  
vr = PyVideoReader(path, target_width=224, target_height=224, filter="scale=256:256")

# ✅ Correct: Use only one method
vr = PyVideoReader(path, target_width=224, target_height=224)

# Resize to fixed 224x224
vr = PyVideoReader(path, target_width=224, target_height=224)

# With custom scaling algorithm
vr = PyVideoReader(path, target_width=224, target_height=224, resize_algo="lanczos")

# ✅ This works: non-scale filter + target dimensions
vr = PyVideoReader(path, filter="format=yuv420p", target_width=224, target_height=224)

# These produce similar results for 16:9 video:
vr = PyVideoReader(path, resize_shorter_side=256)  # → 455x256
vr = PyVideoReader(path, filter="format=yuv420p,scale=w=455:h=256:flags=fast_bilinear")

# Fixed square output - two equivalent methods:
vr = PyVideoReader(path, target_width=256, target_height=256)  # Simpler, recommended
vr = PyVideoReader(path, filter="format=yuv420p,scale=w=256:h=256:flags=fast_bilinear")

vr = PyVideoReader(path, filter="format=yuv420p,scale=w=224:h=224:flags=lanczos")

# All these work correctly:
frames = vr.decode()                           # Decode all
batch = vr.get_batch([0, 10, 20])             # Random access
batch = vr.get_batch([0, 10, 20], with_fallback=False)  # Seek-based
for frame in vr:                               # Iteration
    pass

from video_reader import PyVideoReader

videoname = "/path/to/your/video.mp4"
vr = PyVideoReader(videoname, device='cuda')

vr = PyVideoReader(videoname, device='cuda', filter='scale_cuda:h=512:w=-1:passthrough=0,hwdownload,format=nv12', resize_shorter_side=512)

vr = PyVideoReader(videoname, device='vaapi', filter='hwmap,format=nv12')

from video_reader import PyVideoReader
from time import time

def bench_video_decode(filename, compress_factor, resize):
    start =  time()
    vr = PyVideoReader(filename, resize_shorter_side=resize, threads=0)
    vid = vr.decode(compression_factor=compress_factor)
    duration = time() - start
    print(f"Duration {duration:.2f}sec")
    return vid

vid = bench_video_decode("sample.mp4", 0.25)
print("video shape:", vid.shape)

# Terminal output:
# Duration 4.81sec
# video shape: (501, 1472, 1472, 3)

from decord import VideoReader

vr = VideoReader("sample.mp4")

# Terminal output:
# terminate called after throwing an instance of 'std::bad_alloc'
#  what():  std::bad_alloc
# [1]    9636 IOT instruction (core dumped)