Revert "[ffmpeg] Fix embedding subtitles (#9063)"
Revert "[ffmpeg] Fix embedding subtitles (#9063)"

This reverts commit ccff2c404d7ea9f5b21ede8ae57bb79feec7eb94.

Fixes #10081.

The new approach breaks embedding subtitles into video-only or
audio-only files. FFMpeg provides a trick: add '?' after the argument of
'-map' so that a missing stream is ignored. For example:

opts = [
    '-map', '0:v?',
    '-c:v', 'copy',
    '-map', '0:a?',
    '-c:a', 'copy',
    # other options...
]

Unfortunately, such a format is not implemented in avconv, either.
I guess adding '-ignore_unknown' if self.basename == 'ffmpeg' is the
best solution. However, the example mentioned in #9063 no longer serves
problematic files, so I can't test it. I'll reopen #9063 and wait for
another example so that I can test '-ignore_unknown'.

ozburo/youtube-dl,codesparkle/youtube-dl,daeseokyoun/youtube-dl,yan12125/youtube-dl,luceatnobis/youtube-dl,misterhat/youtube-dl,oskar456/youtube-dl,vijayanandnandam/youtube-dl,malept/youtube-dl,jbuchbinder/youtube-dl,rg3/youtube-dl,phihag/youtube-dl,gnowxilef/youtube-dl,hakatashi/youtube-dl,Rudloff/youtube-dl,vinegret/youtube-dl,misterhat/youtube-dl,luceatnobis/youtube-dl,remitamine/youtube-dl,erikdejonge/youtube-dl,rrooij/youtube-dl,ping/youtube-dl,rg3/youtube-dl,stannynuytkens/youtube-dl,mcepl/youtube-dl,pim89/youtube-dl,ping/youtube-dl,aeph6Ee0/youtube-dl,Tithen-Firion/youtube-dl,fast90/youtube-dl,oskar456/youtube-dl,Thor77/youtube-dl,vinegret/youtube-dl,codesparkle/youtube-dl,steebchen/youtube-dl,malept/youtube-dl,ozburo/youtube-dl,Rudloff/youtube-dl,fluxw42/youtube-dl,dstftw/youtube-dl,spvkgn/youtube-dl,erikdejonge/youtube-dl,yan12125/youtube-dl,Orochimarufan/youtube-dl,nyuszika7h/youtube-dl,marcwebbie/youtube-dl,unreal666/youtube-dl,kidburglar/youtube-dl,spvkgn/youtube-dl,gnowxilef/youtube-dl,pim89/youtube-dl,coreynicholson/youtube-dl,remitamine/youtube-dl,TRox1972/youtube-dl,longman694/youtube-dl,phihag/youtube-dl,nickleefly/youtube-dl,coreynicholson/youtube-dl,nickleefly/youtube-dl,hakatashi/youtube-dl,vijayanandnandam/youtube-dl,aeph6Ee0/youtube-dl,epitron/youtube-dl,mxamin/youtube-dl,TRox1972/youtube-dl,jbuchbinder/youtube-dl,Tatsh/youtube-dl,gkoelln/youtube-dl,Orochimarufan/youtube-dl,stannynuytkens/youtube-dl,Thor77/youtube-dl,jcoady9/youtube-dl,dstftw/youtube-dl,longman694/youtube-dl,mcepl/youtube-dl,Tatsh/youtube-dl,rrooij/youtube-dl,marcwebbie/youtube-dl,mxamin/youtube-dl,steebchen/youtube-dl,gkoelln/youtube-dl,epitron/youtube-dl,Tithen-Firion/youtube-dl,daeseokyoun/youtube-dl,jcoady9/youtube-dl,fluxw42/youtube-dl,unreal666/youtube-dl,nyuszika7h/youtube-dl,fast90/youtube-dl,kidburglar/youtube-dl