AAC bitrate

[kaz219]

Hi,

I'm trying to extract an audio track from a VOB file. I'm encoding it in AAC 128kbps. But in the terminal I see:

size=   67552kB time=2927.1 bitrate= 189.1kbits/s

So the bitrate seem much higher. It is happening with VBR and CBR.

[macr0t0r]

Finally got my account confirmed so I can post. Strange that nobody else has replied to this.

I confirmed this glitch. It only occurs while converting from VOB to XVID (MP4) ffmpeg. No matter what I set for bitrate, frequency and varying (CBR, ABR, VBR), the AAC audio always ends up to be around 189kbps. A pity, since the iPod can only handle 160kbps. I get a lot of audio cuts when I play it back.

However, if I use any other type of source file, it has no problem. Only VOBs show the error. Strange. For the meantime, I suggest you pick up a copy of HandBrake to take care of encoding VOBs (they have to be properly set up in a VIDEO_TS folder). The only other suggestion I have is to first encode to MP4 with the glitch, then re-encode that file using video-passthrough and re-encode the audio to the desired settings. That's an ugly hack that involves re-encoding the audio twice.

The only other solution is to first de-mux the vob and then encode the video and audio files separately.

- macr0t0r

[kaz219]

actually, it seems that the problem is in the AAC encoder, because even trying to extract only the AAC from the VOB file doesn't solve the problem.

I prefer ffmpegX, because it has a better quality/size ratio for H.264 format I find. I can reencode the AAC. Anyway, if I reencode 187kbps into 128kbps, I don't think I loose a lot of quality...