Hello folks
I am encoding music to ogg vorbis format for the first time. From what
i have researched, ogg vorbis is natively a vbr format. Also encoding
using the -q switch is encouraged instead of specifying a bitrate
through -b.
Now, while encoding using -b i get this:
Encoding "file.wav" to
"file.ogg"
at approximate bitrate 224 kbps (VBR encoding enabled)
Notice the VBR encoding enabled message.
But when i specify a quality through -q, no VBR encoding enabled message
is displayed, and mediainfo http://mediainfo.sourceforge.net/ also
displays the Bit rate mode as Constant.
So, what should i do to get VBR encoded files instead of CBR.
Thanks.
> But when i specify a quality through -q, no VBR encoding enabled message-b is equivalent to -q with a quality level chosen based on an approximate bitrate relationship. Both are VBR. CBR is used only if bitrate management is also explicitly requested. The VBR message is only there so that users don't freak out if -b doesn't deliver the exact file size they'd expect from a CBR file.> is displayed, and mediainfo http://mediainfo.sourceforge.net/ also > displays the Bit rate mode as Constant.I would think mediainfo is simply confused. There's no such thing as hard CBR in Vorbis (the behavior is emulated) so there's no way it could simply look at a Vorbis file and say 'this is CBR'. Monty> > So, what should i do to get VBR encoded files instead of CBR. > > Thanks. > _______________________________________________ > Vorbis mailing list > Vorbis at xiph.org > http://lists.xiph.org/mailman/listinfo/vorbis >
On Mon, Jun 20, 2011 at 01:12:08PM -0400, xiphmont at xiph.org wrote:> > Thanks a lot. So I should just use the -q option? > > Sure. Use what's convenient, -q will give you VBR like you want, so will -b :-) > > > Also, i'll report this to the mediainfo author. > > Yes. You could also have him/them contact us if they want more information. > > MontyI have filed a bug report here: http://sourceforge.net/tracker/?func=detail&aid=3323303&group_id=86862&atid=581181 ps: Sorry, i forgot to cc my previous message to the mailing list.
On Mon, Jun 20, 2011 at 11:28:35PM +0530, gt wrote:> I have filed a bug report here: > > http://sourceforge.net/tracker/?func=detail&aid=3323303&group_id=86862&atid=581181Well the bug report was rejected by the mediainfo author, and here's the reason he gave: ---------------------------------------------------------------------- zenitram(Jerome Martinez) said: Vorbis header has this: 0000001C Identification (30 bytes) 0000001C Signature: 1 (0x01) 0000001D Signature: vorbis 00000023 Version: 0 (0x0) 00000027 Channels: 2 (0x02) 00000028 SamplingRate: 44100 (0xAC44) 0000002C BitRate_Maximum: 0 (0x0) 00000030 BitRate_Nominal: 224000 (0x36B00) 00000034 BitRate_Minimum: 0 (0x0) 00000038 BlockSize_0: 11 (0xB) 00000038 BlockSize_1: 8 (0x8) 00000039 Framing: 1 (0x01) Currently, MediaInfo handles such info as a "goal" of 224 Kbps, i.e. a kind of ABR (Average Bit rate), not a VBR (with 2 pass analysis, 1 st pass to detect needs, 2nd pass for coding high differences) I looked a bit at the bitstream, each packet is between 4000 and 4500 byte long, each granule position difference is around a value of 8000, variation is very very tiny... So I see no reason to set it as VBR (or I should also set all CBR MP3s as VBR! MP3 has a bit reservoir in each CBR frame --> this is not pure CBR too...), I put VBR when I detect more differences (extrem example: bitrate at 16 Kbps during 10 seconds then 448 Kbps during 10 seconds, average of 224 Kbps too and this is really a VBR stream) ----------------------------------------------------------------------