#9064: WebVTT decoder truncates files with STYLE blocks
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Reporter: rschupp | Type: defect
Status: new | Priority: normal
Component: avformat | Version: git-master
Keywords: webvtt | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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If a webvtt file contains STYLE blocks, the webvtt decoder truncates the
file at the first such block. Since these blocks typically occur at the
top of the webvtt file, this results in an empty file (except for the
WEBVTT header line).
Note: This may be related to #8684, though the sample webvtt attached
there is invalid.
How to reproduce:
$ ffmpeg -y -v 9 -loglevel 99 -i sample_in.vtt -c copy sample_out.vtt
ffmpeg version 4.3.1-5 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 10 (Debian 10.2.0-15)
configuration: --prefix=/usr --extra-version=5 --toolchain=hardened
--libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu
--arch=amd64 --enable-gpl --disable-stripping --enable-avresample
--disable-filter=resample --enable-gnutls --enable-ladspa --enable-libaom
--enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca
--enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite
--enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-
libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-
libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus
--enable-libpulse --enable-librabbitmq --enable-librsvg --enable-
librubberband --enable-libshine --enable-libsnappy --enable-libsoxr
--enable-libspeex --disable-libsrt --enable-libssh --enable-libtheora
--enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx
--enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2
--enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-
omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2
--enable-pocketsphinx --enable-libmfx --enable-libdc1394 --enable-libdrm
--enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264
--enable-shared
WARNING: library configuration mismatch
avcodec configuration: --prefix=/usr --extra-version=5
--toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu
--incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl
--disable-stripping --enable-avresample --disable-filter=resample
--enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-
libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-
libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig
--enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm
--enable-libjack --enable-libmp3lame --enable-libmysofa --enable-
libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse
--enable-librabbitmq --enable-librsvg --enable-librubberband --enable-
libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --disable-
libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-
libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack
--enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid
--enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal
--enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx
--enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883
--enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
--enable-version3 --disable-doc --disable-programs --enable-libaribb24
--enable-liblensfun --enable-libopencore_amrnb --enable-libopencore_amrwb
--enable-libtesseract --enable-libvo_amrwbenc
libavutil 56. 51.100 / 56. 51.100
libavcodec 58. 91.100 / 58. 91.100
libavformat 58. 45.100 / 58. 45.100
libavdevice 58. 10.100 / 58. 10.100
libavfilter 7. 85.100 / 7. 85.100
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
libpostproc 55. 7.100 / 55. 7.100
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
'sample_in.vtt'.
Reading option '-c' ... matched as option 'c' (codec name) with argument
'copy'.
Reading option 'sample_out.vtt' ... 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 sample_in.vtt.
Successfully parsed a group of options.
Opening an input file: sample_in.vtt.
[NULL @ 0x5569603be0c0] Opening 'sample_in.vtt' for reading
[file @ 0x5569603beb80] Setting default whitelist 'file,crypto,data'
Probing webvtt score:100 size:362
[webvtt @ 0x5569603be0c0] Format webvtt probed with size=2048 and
score=100
[webvtt @ 0x5569603be0c0] Before avformat_find_stream_info() pos: 55 bytes
read:362 seeks:0 nb_streams:1
[webvtt @ 0x5569603be0c0] All info found
[webvtt @ 0x5569603be0c0] stream 0: start_time: NOPTS duration: NOPTS
[webvtt @ 0x5569603be0c0] format: start_time: NOPTS duration: NOPTS
(estimate from bit rate) bitrate=0 kb/s
[webvtt @ 0x5569603be0c0] After avformat_find_stream_info() pos: 55 bytes
read:362 seeks:0 frames:0
Input #0, webvtt, from 'sample_in.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 sample_out.vtt.
Applying option c (codec name) with argument copy.
Successfully parsed a group of options.
Opening an output file: sample_out.vtt.
[file @ 0x5569603c4140] Setting default whitelist 'file,crypto,data'
Successfully opened the file.
Output #0, webvtt, to 'sample_out.vtt':
Metadata:
encoder : Lavf58.45.100
Stream #0:0, 0, 1/1000: Subtitle: webvtt
Stream mapping:
Stream #0:0 -> #0:0 (copy)
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= 0kB time=00:00:00.00 bitrate=N/A speed= 0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: unknown
Input file #0 (sample_in.vtt):
Input stream #0:0 (subtitle): 0 packets read (0 bytes);
Total: 0 packets (0 bytes) demuxed
Output file #0 (sample_out.vtt):
Output stream #0:0 (subtitle): 0 packets muxed (0 bytes);
Total: 0 packets (0 bytes) muxed
Output file is empty, nothing was encoded (check -ss / -t / -frames
parameters if used)
0 frames successfully decoded, 0 decoding errors
[AVIOContext @ 0x5569603c43c0] Statistics: 0 seeks, 1 writeouts
[AVIOContext @ 0x5569603c6fc0] Statistics: 362 bytes read, 0 seeks
--
Ticket URL: <https://trac.ffmpeg.org/ticket/9064>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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