[FFmpeg-trac] #8684(ffmpeg:new): WebVTT decoder breaks when ::cue elements are used
FFmpeg
trac at avcodec.org
Tue May 26 22:48:00 EEST 2020
#8684: WebVTT decoder breaks when ::cue elements are used
--------------------------------+--------------------------------------
Reporter: derrod | Type: defect
Status: new | Priority: minor
Component: ffmpeg | Version: git-master
Keywords: webvtt | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
--------------------------------+--------------------------------------
Summary of the bug: WebVTT input is not read past `::cue` tags in input
file.
How to reproduce:
{{{
% ffmpeg -y -v 9 -loglevel 99 -i test_input.vtt test_output.ass
ffmpeg version git-2020-05-25-6268034 Copyright (c) 2000-2020 the FFmpeg
developers
built with gcc 9.3.1 (GCC) 20200523
configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-
fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-
libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg
--enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr
--enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvpx
--enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265
--enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp
--enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvo-
amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-
libaom --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-
cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec
--enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
libavutil 56. 49.100 / 56. 49.100
libavcodec 58. 87.101 / 58. 87.101
libavformat 58. 43.100 / 58. 43.100
libavdevice 58. 9.103 / 58. 9.103
libavfilter 7. 83.100 / 7. 83.100
libswscale 5. 6.101 / 5. 6.101
libswresample 3. 6.100 / 3. 6.100
libpostproc 55. 6.100 / 55. 6.100
Splitting the commandline.
Reading option '-y' ... matched as option 'y' (overwrite output files)
with argument '1'.
Reading option '-v' ... matched as option 'v' (set logging level) with
argument '9'.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging
level) with argument '99'.
Reading option '-i' ... matched as input url with argument
'test_input.vtt'.
Reading option 'test_output.ass' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option y (overwrite output files) with argument 1.
Applying option v (set logging level) with argument 9.
Successfully parsed a group of options.
Parsing a group of options: input url test_input.vtt.
Successfully parsed a group of options.
Opening an input file: test_input.vtt.
[NULL @ 0000025fa3a9ccc0] Opening 'test_input.vtt' for reading
[file @ 0000025fa3a9dd40] Setting default whitelist 'file,crypto,data'
Probing webvtt score:100 size:139
[webvtt @ 0000025fa3a9ccc0] Format webvtt probed with size=2048 and
score=100
[webvtt @ 0000025fa3a9ccc0] Before avformat_find_stream_info() pos: 44
bytes read:139 seeks:0 nb_streams:1
[webvtt @ 0000025fa3a9ccc0] All info found
[webvtt @ 0000025fa3a9ccc0] stream 0: start_time: -9223372036854776.000
duration: -9223372036854776.000
[webvtt @ 0000025fa3a9ccc0] format: start_time: -9223372036854.775
duration: -9223372036854.775 (estimate from bit rate) bitrate=0 kb/s
[webvtt @ 0000025fa3a9ccc0] After avformat_find_stream_info() pos: 44
bytes read:139 seeks:0 frames:0
Input #0, webvtt, from 'test_input.vtt':
Duration: N/A, bitrate: N/A
Stream #0:0, 0, 1/1000: Subtitle: webvtt
Successfully opened the file.
Parsing a group of options: output url test_output.ass.
Successfully parsed a group of options.
Opening an output file: test_output.ass.
[file @ 0000025fa3aa1b80] Setting default whitelist 'file,crypto,data'
Successfully opened the file.
Output #0, ass, to 'test_output.ass':
Metadata:
encoder : Lavf58.43.100
Stream #0:0, 0, 1/100: Subtitle: ass (ssa)
Metadata:
encoder : Lavc58.87.101 ssa
Stream mapping:
Stream #0:0 -> #0:0 (webvtt (native) -> ass (ssa))
Press [q] to stop, [?] for help
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless
if it occurs once at the start per stream)
No more output streams to write to, finishing.
size= 1kB time=00:00:00.00 bitrate=N/A speed= 0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:1kB
muxing overhead: unknown
Input file #0 (test_input.vtt):
Input stream #0:0 (subtitle): 0 packets read (0 bytes); 0 frames
decoded;
Total: 0 packets (0 bytes) demuxed
Output file #0 (test_output.ass):
Output stream #0:0 (subtitle): 0 frames encoded; 0 packets muxed (0
bytes);
Total: 0 packets (0 bytes) muxed
0 frames successfully decoded, 0 decoding errors
[AVIOContext @ 0000025fa3aa2d40] Statistics: 0 seeks, 1 writeouts
[AVIOContext @ 0000025fa3aa5fc0] Statistics: 139 bytes read, 0 seeks
}}}
The entire content of the input file is as follows (also attached):
{{{
WEBVTT
::cue(.white){ color: white; }
1
00:00:01.000 --> 00:00:05.000 line:77% position:50% align:middle
<c.white>Hello World</c>
}}}
The output file only contains the boilerplate ASS information and no
events. (see attached file).
Removing the line(s) starting with `::cue` will result in a successfully
converted output (albeit without the styling).
Note that even a codec copy from WebVTT to WebVTT will fail and produce an
output file that contains only the "WEBVTT" header (other attached file).
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8684>
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