HOW TO convert RealMedia to other formats

Background

Around about 1995 RealNetworks (tm), Inc. started out with Real Audio. It is a psycho acoustic, bit decimating audio encoder which guarantees to not exceed the specified bandwidth. In listening tests it is excellent. Then RealVideo came along, doing the same for video. It seems to perform better at lower bitrates than MPEG1 does. Ideal for the internet. It saw off Vivo, or was that acquired by RealNetworks? Anyway, RealMedia software is smart and useful.

Problem

The only problem with it is that occasionally rare clips turn up and it would be useful to turn them into other formats, such as MPEG1 for eventual conversion to Video CD, but RealMedia is a proprietory format. As far as I know its audio and video coding scheme has never been published.

How do we convert these clips?

Conversion programs

I don't know the legality of these programs, but they can convert RealMedia files to .AVIs and uncompressed .WAV files!

Tinra
Tinra is released under the GNU public license. It writes the Real Video file to .AVI using any AVI codec. It can reliably decode RealVideo clips although it really needs its temporiser initialised to adjust the frame rate to keep the audio in sync with the video. For clips with audio and video using the temporiser it uses 3 passes, I think that it merges the time base corrected audio and video output on the third pass.

RA2WAV
RA2WAV converts the sound from RealMedia clips to uncompressed WAV files. It doesn't work with the SureStream format. I don't know if it still supported, but it is pretty good.

Saving streaming data to the hard disk

StreamBox VCR Suite v2.0
Streambox VCR
This is not so much a conversion tool but a way to save streamed Real Audio, .WMA, QuickTime and other formats to your hard disk for playback later. It is illegal for US citizens to use this software!

This is an ultra useful program. Eventually Real Networks will change the coding scheme or server software so that this program won't work any more, but it works for now!

Recording streaming audio to the hard disk

To record just audio it is possible to use a sample recorder application such as CoolEdit to record from the WAV output of the soundcard while playing streamed RealAudio or RealAudio clips. This can produce good results and then the audio can be processed just like a normal WAV. This can be particularly good for recording sounds from radio stations that use Real Audio over the web.

How to get pictures from Media Players (and DirectX programs)

It is very difficult to snatch frames from Media Players because they tend to use DirectX overlays which are not drawn by GDI. There is an EnumSurfaces function on IDirectDraw4 but it doesn't seem to work across processes.

To snatch the surface directly requires reading video memory and is a low level operation. Thankfully HyperSnap-DX 4 does this for us!
Download an evaluation version from the Hyperionics web site.

Analysis

I thought that such programs would be impossible because the Real Media coding schemes seem to be a closely guarded secret. Their streaming protocol is a modified version of the public RTSP (Real Time Streaming Protocol) format. My attempt using the Multimedia Control Interface to record the audio to .WAV while the clip is playing in RealAudio didn't work very well and grabbing frames while RealPlayer is running is a non-starter. Tinra, RA2WAV and Streambox VCR properly decode the stream, which is ideal.

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