similar to: AW: Keyframe seeking in Ogg and spec

Folks have noticed that the documentation is semi-silent about how to properly encode the granule position and interleave synchronization of keyframe-based video. The primary reasons for this: a) we at Xiph hadn't had to do it yet b) there are several easy possibilities, and the longer we had to think about it before mandating One True Spec, the better that spec would likely be. The

Question: is it permissible to put more than one frame packet into a page? At 30 fps, Ogg page overhead is on the order of 8 - 10 kbits/sec. At low datarates, this is going to be unacceptable. If I shove a few frames into a page, how does this affect the granulepos stuff? ___ Dan Miller (++,) Founder, On2 Technologies <p>--- >8 ---- List archives: http://www.xiph.org/archives/

Dear all I'm aware that there have been several discussions about the seeking issue and I'm sorry to bring this up again. To solve the problem with Inter-Frame garbage, a seek to the previous keyframe has to be made. The keyframe number should be extracted from the granulepos of the frame where we want to seek to. I hope I understood the theory - unfortunately a few questions have

Ups! Maybe it's time somebody corrected that statement then - the wiki seems the right place to put the correct algorithm, IMHO. Cheers, Silvia. On Feb 13, 2008 10:06 AM, Ralph Giles <ralph.giles@artifex.com> wrote: > > On 12-Feb-08, at 2:57 PM, Ralph Giles wrote: > > > http://wiki.xiph.org/index.php/GranulePosAndSeeking > > I'm not sure it's helpful to

> No particular answers, but I can at least point out that the way > things were designed for CMML was to work with the existing Ogg > seeking algorithm. The idea is that a generic seeking routine can work > on any Ogg file, as long as it knows the granulepos->time mapping for > the logical bitstreams in the file. That's why all the > timestamp-related info is crammed into

Hi all, I'm actually learning how to use ogg, theora and vorbis. My idea is to create a small program running, that is able to concatenate ogg video+audio files. However I have some small questions. Here I will start with the first one: I read the following for seeking in ogg for a theora key-frame: ---- snipp (http://www.xiph.org/ogg/doc/ogg-multiplex.html) ---- [...]The third point

David Flynn has proposed a new Ogg Dirac mapping. The draft is here: http://davidf.woaf.net/dirac-mapping-ogg.pdf This is a much bigger break from other codecs than my draft (at http://wiki.xiph.org/index.php/OggDirac). We talked a bit about it on IRC today. Below is my summary; hopefully David can correct anything I got wrong or misleading. Comments? There are two main differences

Hi, I am continuing to try to debug my ogg/theora decoder. The issue seems to be that not enough packets are being pulled from the bitstream, here is some sample output from my player with some debugging comments put in: (playback began at first frame, this is from the middle of the clip) get page at 1765027 got packet frame++, skip is 0 frame decoded page processed, kframe=414 : offs=442 get

Hi, sorry, there is a bug in the CMML spec and wiki page ... I discussed this with Silvia earlier this week but haven't gotten around to correcting it yet. CMML granulepos is much like theora's; the previous granule is stored in the higher bits, and the delta since then is stored in the lower bits. The current timestamp is the sum of the two. This is the behavior of the implementations

After some more thought on this, I'm trying to work out whether the back link offset needs precision. Semantically, the only need we have for this is to be able to seek back to a point before the start of the earliest event still active at the time of the original seek. As far as I know, and please correct me if I'm wrong, nothing in Ogg mandates that this backlink actually resolves to a

Hello, I'm just totally confused. In my theora streams encoded using ffmpeg2theora (but also when using my own encoder) I have packets with a granulepos of -1 so I can't identify the packet during a seeking operation correctly. I can also see those strange value when I just print the packet granulepos before sending it to the Theora decoder. I know why there are PAGES with granularpos of

I've developed an indexer which embeds a keyframe index track in Ogg files. It embeds the index in its own track, so that players that don't understand or don't want to use the index can just ignore it. Ogg needs this to make seeking over networks faster and more efficient. Currently we must do a bisection search when seeking, which usually takes aound 6 HTTP requests, give or

> The advantage of storing this in the granulepos field itself, like > theora and CMML do, is that the seek code may already understand how > to handle the back pointer. Right now everything assumes the mapping > is from 'initialized decoder' + 'granulepos from page header' => > timestamp, or in the case of theora and CMML => 'timestamp' + 'last

On Sat, 2006-07-15 at 14:35 -0700, Ralph Giles wrote: > On Sat, Jul 15, 2006 at 02:17:22PM -0500, Joe Wreschnig wrote: > > > I'm working on support for tagging Speex files for Mutagen[0] and part > > of the specification at [1] is confusing me. It says the first page > > should have granulepos 0 and packetno 0. Does this really mean page > > sequence number 0,

(Sending again after subscribing, I guess the moderator is on vacation.) I'm working on support for tagging Speex files for Mutagen[0] and part of the specification at [1] is confusing me. It says the first page should have granulepos 0 and packetno 0. Does this really mean page sequence number 0, since the Ogg format doesn't number packets? If it doesn't mean page sequence number,

Hi, I have a question about seeking. In fact, it's more or less a kind of rambling and thinking aloud, circling around a question. I've been wondering how to deal with seeking in a stream, and what to do when seeking in the middle of a set of active events (eg, when several bits of text are supposed to be shown, but you seek after the time when they are first shown, and before the time

Hi, I have modified fenice(streaming server) and mplayer(media client) code to support for ogg container(vorbis+theora). Now I have to implement forward and rewind of an ogg(vorbis+theora)file by time. So I would like to do file seek to start reading the file from that position. Eg:- mplayer will send +10 secs to forward request to fenice through RTSP and fenice should read and send packets from

Hi, I have modified fenice(streaming server) and mplayer(media client) code to support for ogg container(vorbis+theora). Now I have to implement forward and rewind of an ogg(vorbis+theora)file by time. So I would like to do file seek to start reading the file from that position. Eg:- mplayer will send +10 secs to forward request to fenice through RTSP and fenice should read and send packets from

Hello, > (1) Split the content into chain segments > (2) extract the first and last data packet from each segment, for all tracks > (3) recover / calculate the granulepos values for the first and last data packets (*) > (4) convert the granulepos values from the first and last data packets into time values > (5) take the largest difference between start and end time as the total

I am trying to figure out how theora timestamps map to absolute time values. This information would be needed to seek by 1 sec, 5 secs etc. I understand the granulepos is interpreted as Absolute number of key frames so far | number of frames since last key frame. E.g. 1000|1, 1000|2, ... How does this map to absolute time in millisecs since the start, I can think of the following formula: Total