我正在尝试将 gif 同步到 Spotify 上播放的音乐节拍，但这样做时遇到了速度问题。我一定要疯了，因为我找不到为什么这不起作用的原因。以下是我的方法:
BPS)BPS = BPM / 60 SPB ) 中找到 Seconds/Beat ( BPS )SPB = 1 / BPS SPL) 的数量来找到秒/循环 (BPL)SPL = SPB * BPL SPL) 转换为毫秒/循环 (MSPL)MSPL = SPL * 1000 MSPL ) 除以 .gif 中的帧数 ( num_frames ) 以找到一帧所需的时间 ( frame_time )，四舍五入到最接近的偶数，因为 .gif 帧时间是只精确到整毫秒frame_time = MSPL / num_frames actual_duration ) 相加并循环帧加或减 1 毫秒，直到 actual_duration匹配 ceil(MSPL) (始终优先考虑较长的实际持续时间而不是较短的持续时间)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 的实际毫秒/循环应该始终等于 MSLP 或大于 MSLP。但是，当我使用指定的帧时间保存 .gif 时，如果校正值不为 0，则 .gif 始终以比预期更快的速度播放。我注意到，当使用提供相同“将 gif 同步到音乐”功能的其他在线服务时，情况也是如此；所以我认为不仅仅是我发疯了。
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
我正在使用 PIL (Pillow) 的图像模块保存 gif:
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)
我在这里做错了什么吗？我似乎无法找出为什么这不起作用以及为什么 gif 的实际持续时间比指定的帧时间短得多。提供此功能的其他站点/服务最终得到相同的结果让我感觉稍微好一些，但同时我觉得这绝对应该是可能的。
最佳答案
解决了!我不知道这是 .gif 格式的限制，还是 PIL 中 Image 模块的限制，但似乎帧时间只能精确到 10 毫秒的倍数。在检查修改后的图像的实际帧时间时，它们被限制到最接近的 10 倍数，从而导致整体播放速度比预期的要快。
为了解决这个问题，我修改了代码以选择以 10 为增量的帧时间(如果需要，再次优先考虑更长的实际持续时间)并在整个列表中尽可能均匀地分散帧时间调整:
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
关于python - 将 GIF 与音乐节奏同步导致持续时间比预期的要短，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/62136055/