Fixed compile error with ffmpeg-5.0.

[bchoineubility]

🦟 Bug fix

Fixes #579

Summary

When I try to build with ffmpeg-5.0, it occurred compile error by comparing patch [PATCH] Fix compatibility with FFmpeg 5.0 (#325)

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[mjcarroll]

Since this was originally released to support Ubuntu 18.04 Bionic, I think that we need to continue to maintain support for older versions of libav, in this case you should be able to do it like

#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(59, 24, 100)
        int numChannels = this->dataPtr->codecCtx->ch_layout.nb_channels;
#else
        int numChannels = this->dataPtr->codecCtx->channels;
#endif

[bchoineubility]

Since this was originally released to support Ubuntu 18.04 Bionic, I think that we need to continue to maintain support for older versions of libav, in this case you should be able to do it like

#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(59, 24, 100)
        int numChannels = this->dataPtr->codecCtx->ch_layout.nb_channels;
#else
        int numChannels = this->dataPtr->codecCtx->channels;
#endif

@mjcarroll I close this PR and apply your suggestion and open PR again. thanks.