我正在尝试将gif与Spotify上播放的音乐节拍同步，但我在同步时遇到了速度问题。我一定是疯了，因为我找不到为什么不能工作的原因。以下是我的方法。
BPS)BPS = BPM / 60SPB)的BeatsSecond (BPS)SPB = 1 / BPSSPL)乘以BeatsLoop的数量(BPL)中的.gifSPL = SPB * BPLSPL)到毫秒循环(MSPL)MSPL = SPL * 1000MSPL)乘以帧数(num_frames)中的.gif来计算一帧所需的时间(frame_time)，四舍五入到最接近的偶数，因为.gif帧时间最多只能精确到整毫秒。frame_time = MSPL / num_framesactual_duration)，并在各帧中循环加减1毫秒，一直到 actual_duration 匹配 ceil(MSPL) (总是优先考虑较长的实际期限而不是较短的期限)difference = MSPL - actual_duration if not math.isclose(0, difference): # Add the difference and always prioritize longer duration compared to real duration value correction = int(math.ceil(difference)) for i in range(0, abs(correction)): # Add/subtract corrections as necessary to get actual duration as close as possible to calculated duration frame_times[i % len(frame_times)] += math.copysign(1, correction)
现在，从这一点来看，gif的实际MillisecondsLoop应该总是等于MSLP或大于MSLP。然而，当我用指定的帧时间保存.gif时，如果修正值不是0，那么.gif总是以比预期更快的速度播放。我注意到，当使用其他在线服务，提供相同的 "同步gif到音乐 "功能，也是这种情况，所以它不只是我疯了，我想。
下面是用于获取帧时间的实际代码。
def get_frame_times(tempo: float, beats_per_loop: int, num_frames: int):
# Calculate the number of seconds per beat in order to get number of milliseconds per loop
beats_per_sec = tempo / 60
secs_per_beat = 1 / beats_per_sec
duration = math.ceil(secs_per_beat * beats_per_loop * 1000)
frame_times = []
# Try to make frame times as even as possible by dividing duration by number of frames and rounding
actual_duration = 0
for _ in range(0, num_frames):
# Rounding method: Bankers Rounding (round to the nearest even number)
frame_time = round(duration / num_frames)
frame_times.append(frame_time)
actual_duration += frame_time
# Add the difference and always prioritize longer duration compared to real duration value
difference = duration - actual_duration
if not math.isclose(0, difference):
correction = int(math.ceil(difference))
for i in range(0, abs(correction)):
# Add/subtract corrections as necessary to get actual duration as close as possible to calculated duration
frame_times[i % len(frame_times)] += math.copysign(1, correction)
return frame_times
我是用PIL(Pillow)的图像模块来保存gif的。
frame_times = get_frame_times(tempo, beats_per_loop, num_frames)
frames = []
for i in range(0, num_frames):
# Frames are appended to frames list here
# disposal=2 used since the frames may be transparent
frames[0].save(
output_file,
save_all=True,
append_images=frames[1:],
loop=0,
duration=frame_times,
disposal=2)
我有什么地方做错了吗？我似乎找不到为什么这样做不行，为什么gif的实际持续时间比指定的帧时间短很多。这让我感觉稍微好一点，其他提供这个功能的网站服务最终也是同样的结果，但同时我觉得这绝对应该是可能的。
解决了! 我不知道这是.gif格式的限制还是PIL中图像模块的限制，但似乎帧时间只能精确到10毫秒的倍数。经检查修改后的图像的实际帧时间，它们被浮动到最接近10的倍数，导致整体播放速度比预期快。
为了解决这个问题，我修改了代码，以10为增量选择帧时间（必要时再次优先选择较长的实际持续时间），并将帧时间调整尽可能均匀地分散在整个列表中。
def get_frame_times(tempo: float, beats_per_loop: int, num_frames: int):
# Calculate the number of seconds per beat in order to get number of milliseconds per loop
beats_per_sec = tempo / 60
secs_per_beat = 1 / beats_per_sec
duration = round_tens(secs_per_beat * beats_per_loop * 1000)
frame_times = []
# Try to make frame times as even as possible by dividing duration by number of frames
actual_duration = 0
for _ in range(0, num_frames):
frame_time = round_tens(duration / num_frames)
frame_times.append(frame_time)
actual_duration += frame_time
# Adjust frame times to match as closely as possible to the actual duration, rounded to multiple of 10
# Keep track of which indexes we've added to already and attempt to split corrections as evenly as possible
# throughout the frame times
correction = duration - actual_duration
adjust_val = int(math.copysign(10, correction))
i = 0
seen_i = {i}
while actual_duration != duration:
frame_times[i % num_frames] += adjust_val
actual_duration += adjust_val
if i not in seen_i:
seen_i.add(i)
elif len(seen_i) == num_frames:
seen_i.clear()
i = 0
else:
i += 1
i += num_frames // abs(correction // 10)
return frame_times