yt-dlp/yt_dlp/postprocessor/mp4direct.py

133 lines
5 KiB
Python
Raw Normal View History

2022-07-14 00:03:39 +00:00
import os
2022-06-11 07:13:21 +00:00
from math import inf
from .common import PostProcessor
from ..utils import prepend_extension
from ..mp4_parser import (
write_mp4_boxes,
parse_mp4_boxes,
pack_be32,
pack_be64,
unpack_ver_flags,
unpack_be32,
unpack_be64,
)
class MP4FixupTimestampPP(PostProcessor):
@property
def available(self):
return True
def analyze_mp4(self, filepath):
""" returns (baseMediaDecodeTime offset, sample duration cutoff) """
2022-06-11 07:13:21 +00:00
smallest_bmdt, known_sdur = inf, set()
with open(filepath, 'rb') as r:
for btype, content in parse_mp4_boxes(r):
if btype == 'tfdt':
version, _ = unpack_ver_flags(content[0:4])
# baseMediaDecodeTime always comes to the first
if version == 0:
bmdt = unpack_be32(content[4:8])
else:
bmdt = unpack_be64(content[4:12])
if bmdt == 0:
continue
smallest_bmdt = min(bmdt, smallest_bmdt)
elif btype == 'tfhd':
version, flags = unpack_ver_flags(content[0:4])
if not flags & 0x08:
# this box does not contain "sample duration"
continue
# https://github.com/gpac/mp4box.js/blob/4e1bc23724d2603754971abc00c2bd5aede7be60/src/box.js#L203-L209
# https://github.com/gpac/mp4box.js/blob/4e1bc23724d2603754971abc00c2bd5aede7be60/src/parsing/tfhd.js
sdur_start = 8 # header + track id
if flags & 0x01:
sdur_start += 8
if flags & 0x02:
sdur_start += 4
# the next 4 bytes are "sample duration"
sample_dur = unpack_be32(content[sdur_start:sdur_start + 4])
known_sdur.add(sample_dur)
maximum_sdur = max(known_sdur)
for multiplier in (0.7, 0.8, 0.9, 0.95):
sdur_cutoff = maximum_sdur * multiplier
if len(set(x for x in known_sdur if x > sdur_cutoff)) < 3:
break
else:
2022-06-11 07:13:21 +00:00
sdur_cutoff = inf
return smallest_bmdt, sdur_cutoff
2022-07-14 00:03:39 +00:00
@staticmethod
def transform(r, bmdt_offset, sdur_cutoff):
for btype, content in r:
if btype == 'tfdt':
version, _ = unpack_ver_flags(content[0:4])
if version == 0:
bmdt = unpack_be32(content[4:8])
else:
bmdt = unpack_be64(content[4:12])
if bmdt == 0:
yield (btype, content)
continue
# calculate new baseMediaDecodeTime
bmdt = max(0, bmdt - bmdt_offset)
# pack everything again and insert as a new box
if version == 0:
bmdt_b = pack_be32(bmdt)
else:
bmdt_b = pack_be64(bmdt)
yield ('tfdt', content[0:4] + bmdt_b + content[8 + version * 4:])
continue
elif btype == 'tfhd':
version, flags = unpack_ver_flags(content[0:4])
if not flags & 0x08:
yield (btype, content)
2022-07-14 00:03:39 +00:00
continue
sdur_start = 8
if flags & 0x01:
sdur_start += 8
if flags & 0x02:
sdur_start += 4
sample_dur = unpack_be32(content[sdur_start:sdur_start + 4])
if sample_dur > sdur_cutoff:
sample_dur = 0
sd_b = pack_be32(sample_dur)
yield ('tfhd', content[:sdur_start] + sd_b + content[sdur_start + 4:])
continue
yield (btype, content)
2022-07-14 00:03:39 +00:00
def modify_mp4(self, src, dst, bmdt_offset, sdur_cutoff):
with open(src, 'rb') as r, open(dst, 'wb') as w:
write_mp4_boxes(w, self.transform(parse_mp4_boxes(r)))
def run(self, information):
filename = information['filepath']
temp_filename = prepend_extension(filename, 'temp')
self.write_debug('Analyzing MP4')
bmdt_offset, sdur_cutoff = self.analyze_mp4(filename)
2022-06-11 07:13:21 +00:00
working = inf not in (bmdt_offset, sdur_cutoff)
# if any of them are Infinity, there's something wrong
# baseMediaDecodeTime = to shift PTS
# sample duration = to define duration in each segment
self.write_debug(f'baseMediaDecodeTime offset = {bmdt_offset}, sample duration cutoff = {sdur_cutoff}')
2022-06-11 07:13:21 +00:00
if bmdt_offset == inf:
# safeguard
bmdt_offset = 0
self.modify_mp4(filename, temp_filename, bmdt_offset, sdur_cutoff)
if working:
self.to_screen('Duration of the file has been fixed')
else:
self.report_warning(f'Failed to fix duration of the file. (baseMediaDecodeTime offset = {bmdt_offset}, sample duration cutoff = {sdur_cutoff})')
2022-07-14 00:03:39 +00:00
os.replace(temp_filename, filename)
return [], information