What is the fastest and best way to convert an rmvb video to mp4/mkv without losing any quality?

Question

The file will be played in a Popbox3D.

My old method was to convert the video using vidcoder (an offshoot of handbrake) using normal settings, but I've recently confirmed that this significantly reduces video and audio quality.

I bumped up the conversion quality to 'high profile' and this produced a higher quality video but raised the conversion time to about twice the video length (95 minutes to convert a 45 minute video) on a Core2Duo laptop. This is less than ideal when a large number of videos need to be converted.

I have tried a direct remuxing using mkv toolnix but this produced a video that refused to display video on the Popbox3D, which is consistent with the reported:

it is possible to put RealMedia A/V in MKV container (used MKVtoolnix) - however, it is awkward to play later.
RV40 is only suspected to be based on H.264 - simplify, is not consistent with MPEG-4 AVC specification.

I have read that...

Under normal circumstances, [ffmpeg] should convert the video to .video.mp4 and the audio to (.wav then to) .audio.mp4, then mux the video and audio into a new .mp4 file and delete the temporary video-only and audio-only files.

and I am currently attempting to discover how this is done.

Can anyone help me?

PS: I download a lot of series from Asia and for some strange reason, rmvb is a really popular format over there. Sometimes, it's the only format that's available. Unfortunately, it's a format that is incompatible with the Popbox3D, so I have to convert the files before I can watch them on my TV.

Answer 1

Transcoding (what you want to do) can be tricky in terms of quality because of how the program decodes the source material. Better decoders can help, but the best solution is more encoding bitrate (and larger file size).

If you want to use vidcoder but want it to be faster, start with the normal profile and up the bitrate substantially (try quality of 15 or 12). This will be only slightly slower than before but offer much better quality. The same can be done with the audio bitrate (160Kb/s+). The high quality profiles will require more CPU power because of things like b-frames, adaptive quantization, 2-pass bitrate control, CABAC, and various other options, which provide better image quality at lower bitrates.

Quality options may also improve quality even with high bitrates. The processor you are using is.... slow. A computer designed for video editing will be substantially faster, and allow use of better quality control at a realtime bitrate.

If a larger file size is unacceptable, then the tradeoff is better quality settings, which are much slower. If that is still unacceptable, then get a new fast computer ($$$$$).