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Had an interesting glitch yesterday.
mp3 in an avi file was borked. While it would load in the .avs with directshowsource (it errored on AVISource), it would not play any audio if I began playback/encode from frame 0. However, if I advanced it a little bit and played, the audio would play.
When I'd go to do "save wav" in virtualdub, it would save an empty .wav file, even if I tried clipping/saving from a frame higher than 0 to start from. Same thing if I tried to extract out with ffmpeg. Same thing if I tried to open the .avi or .avs in a Sound editor. I couldn't even get the audio out using graphedit.
However, if I opened the .avi directly in Virtualdub, I was able to extract the audio out via "save wave" but there were these error messages:
[!] AVI: Stream 1 (audio) has a non-zero start position of 2 samples (+52 ms).
VirtualDub does not currently support a non-zero start time and the stream
will be interpreted as starting from zero.
[!] AVI: Truncated or invalid MP3 audio format detected (18 bytes, should be
30). Attempting to fix.
[!] AVI: A non-zero wBitsPerSample value was detected in the MP3 audio format
structure. This has been corrected in-memory to zero for better
compatibility with commonly installed MP3 audio codecs.
[!] AVI: Variable bitrate (VBR) audio detected. VBR audio in AVI is
non-standard and you may encounter sync errors up to 0ms when attempting
to extract WAV files or playing in some players. If this is a problem, use
Full Processing mode is recommended to decompress or recompress the audio.
(This warning can be disabled in Options, Preferences, AVI. bitrate: 256.0
± 0.1 kbps)
--I've been using Virtualdub on a regular basis since about the year 2000 and Avisynth since the project began and I've never had an audio stream that was as difficult to process as this one.
Can anyone tell me what was going on here?
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