[FFmpeg-user] Failed to open codec in avformat_find_stream_info

Ted Park kumowoon1025 at gmail.com
Wed Apr 1 09:45:27 EEST 2020


> Oh, I see. So you think the inability to get the subtitle streams is related to the component that accesses the BD? Right? If so, I'm a bit mystified because I don't see how ffmpeg would know which MPLS (playlist file) relates to the M2TSs that I concatenated or even where the MPLS was located on the disc.
> Does that mean I should also point ffmpeg to the particular MPLS? I think I know how to suss out the particular MPLS, but how would I point ffmpeg to it? Or am I completely missing the point -- it would be the first time in the last minute or so. :-)

I was assuming it was a commercial pressed Blu-Ray. If so, then it is most likely copy protected so that for example you can’t just drag the m2ts files from the disc and drop them on your desktop to get a perfect backup or working copy. So if you point at a file on a BDMV disc as if it was on your unencrypted drive, the data is *supposed* to be scrambled, or further encrypted, depending on studio. Or, it can refuse/fail to read, which is also what happens if it hits a region restriction (not so much a problem as it is on DVDs but they exist) Software exists, such as libbluray, that is aware of this storage scheme and handles access to the disc accordingly.

And of course like practically any copy protection scheme in history, the DRM tech’s been reverse-engineered/private-keys-leaked/algorithm-cracked and you can configure your drive with libraries and keys to circumvent it.

The general idea is that unless this is a blank blu-ray that you burned a BDMV filesystem onto, it’s going to stop you from reading it like a normal thumb drive. You said that you concatenated the m2ts files, so I’m a little confused by that though. From the command line I thought you were just pointing at a path on a BDMV disc. If you pull off the files from a commercial blu-ray disc as if it was a regular block device and simply concatenate them by the filename number sequence, they were probably copied in their original mangled state, and with no info about where e.g. the main program is, if there are multiple angles available, which would be in the playlist file.

If this is something you authored yourself, then the drm aspect most likely doesn’t apply, but the part about the data structure on the bdmv disk does, if it was authored to play in regular blu-ray players. Those m2ts files are a bit different from the typical mpeg program streams.

Ted Park

More information about the ffmpeg-user mailing list