ffprobe will output invalid XML

[eelco]

When using XML output for ffprobe, there are cases where ffprobe will output invalid XML.

We have found several cases of files (‘in the wild’) containing metadata causing this problem.

% ffprobe -show_format -print_format xml metadata-with-control-characters.avi > metadata-with-control-characters.xml
ffprobe version N-56246-g16837f9 Copyright (c) 2007-2013 the FFmpeg developers
  built on Sep 12 2013 21:13:18 with llvm-gcc 4.2.1 (LLVM build 2336.11.00)
  configuration: --extra-cflags='-DMACOSX_DEPLOYMENT_TARGET=10.6 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.6' --extra-ldflags='-isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -mmacosx-version-min=10.6'
  libavutil      52. 43.100 / 52. 43.100
  libavcodec     55. 31.101 / 55. 31.101
  libavformat    55. 16.102 / 55. 16.102
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 84.100 /  3. 84.100
  libswscale      2.  5.100 /  2.  5.100
  libswresample   0. 17.103 /  0. 17.103
Input #0, avi, from 'metadata-with-control-characters.avi':
  Metadata:
    artist          : 125
    comment         : ?
    copyright       : 8536
    encoder         : Lavf55.15.100
  Duration: 00:00:01.01, start: 0.000000, bitrate: 9629 kb/s
    Stream #0:0: Video: mpeg4 (Simple Profile) (XVID / 0x44495658), yuv420p, 512x384 [SAR 1:1 DAR 4:3], 29.97 tbr, 29.97 tbn, 29.98 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, s16p, 136 kb/s

In this case a character that is illegal in XML (0x12, see ​http://www.w3.org/TR/REC-xml/#charsets for allowed characters) is not scrubbed from the metadata.

(Using an XML library instead of concatenating strings would prevent these kinds of bugs.)

[eelco]

I’ve added another example of a file that causes invalid XML output from ffprobe.

[cehoyos]

Is this a regression?

[eelco]

Not that I’m aware of. I don’t think it has ever worked correctly, FFmpeg always seems to dump the metadata ‘as is’, which is not really a problem when using it on the command line, but does become a problem when the encoding is explicitly specified (such as in XML).

[cehoyos]

This is apparently a duplicate of ticket #1163 (and maybe #2502), patch sent by Stefano.