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| Sujet : Low Motion+ Mp3 VBR | |
| gilou2 | http://www.virtualdub.org
Dans les anciennes news (il y a un lien en haut des new actuelles). |
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| Vue Rapide de la discussion |
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| gilou2 | http://www.virtualdub.org
Dans les anciennes news (il y a un lien en haut des new actuelles). |
| Erwan_ | thx, tu la pecho ou l'info , j'vais aller y jeter un oeuil pour en savoir plus |
| gilou2 | Ya qu'a lire ça (news de VirtualDub) :
A modified build of VirtualDub recently got posted on the Internet that allows you to multiplex externally encoded MP3s with a video track, to produce an AVI file with VBR (variable bit rate) audio. Although this is not an official build, it sort of works, with only one problem... VBR audio is invalid in an AVI file. The equation that determines audio synchronization in an AVI file is time = audio_sample * block_size / average_bytes_per_second , with block_size and average_bytes_per_second being constant over the entire AVI file. AVI does support VBR streams, but as the Canopus AVI problem showed, the dwSampleSize=0 value doesn't work for audio streams (see below). Couple that with the fact that for the Fraunhofer MP3 format, block_size = 1 byte per sample, and you can see a small problem: AVI forces a rigid relationship between bytes and time. This formula is also the only relationship -- the placement of audio blocks in the file relative to video blocks, or interleaving, makes absolutely no difference in audio sync, and this why "audio skew correction" is the only setting in VirtualDub's audio menu that makes a difference. Yes, you can have VBR audio in an AVI file, and it will play. You'll also find that the greater degree of VBR used, the worse the audio sync can get in local areas. Windows Media Player is especially sensitive to fast variation of bitrate, and you can end up with variations in video playback speed as a side effect of the VBR. I think you can see now why I've not added the ability to mux VBR audio into the mainline codebase. Please do not ask me for this feature, because I'm not going to add it. Sharp observers will point out that MPEG layer III audio is inherently VBR to some extent. This is, in fact, the key to realizing how bad of hack MP3-in-AVI is. MP3 has three features that make it difficult to use in AVI: Bitrates can be switched on the fly, thus modifying the frame size, since frames are always 1152 samples (MPEG-1) or 576 samples (MPEG-2). To hit an exact bitrate at 44.1KHz, the padding bit is toggled periodically, adding or subtracting a single byte off the size of each frame. Unused space in a frame can be used by later ones. This is called the "bit reservoir." The Fraunhofer codec's solution is to avoid varying bitrates, to lie by saying that the compressed block size is one byte, and to silently accumulate bytes until a complete frame can be decompressed. This breaks rigid synchronization at the AVI level, but it works well enough during playback because the ratio of compressed to decompressed data is pretty regular for constant-bitrate streams. Use a VBR stream, however, and you can interfere with smooth buffering in the player. Also, this lie gives you really lousy edits, because the MP3 stream has a granularity hundreds of times worse than the 1-byte block size indicates, and the codec has to discard the fragments that remain. As a result, you can have a terrible time trying to offset the start of an MP3-compressed audio track in an AVI. I recommend not compressing to MP3 until after all your edits are done, or else you can get glitches at the edit points. |
| Erwan_ | Le mp3 vbr c'est pas conseille !! :ouch: L'avantage c'est que ca prend moins de place --> soit ca te laisse plus de place pour la video, soit tu peux augmenter la qualite du mp3. |
| Bruce | Ben le vbr de toute façon c pas conseillé pour la vidéo mais c pour qui voyez ;). |
| Erwan_ | thx mais wavemp3 ca foire ...
En mp3 constant ca marche nickel mais en vbr ca part en couille Sinon, c'est koi le nom exacte de virtual dub pour mp3 vbr |
| Bruce | Pour utiliser un MP3 directement avec vdub :
1) soit on prend une des versions de vdub MP3 qui accèptent le MP3 (chargez le comme un wav...). 2) soit utilisez un soft tel que wavemp3 qui change le header. L'avantage c que ça marche pour toutes les versions de vdub ;) |
| Erwan_ | Ok c'est cool merci [:dux] [:dux] |
| sickBoy73 | j'avais pas vu ton shot !
c pas la version ki gere le mp3 ca, il faut prendre la version modifiee mp3-freeze bonne chance |
| sickBoy73 | bon g essaye et ca marche.
g 'virtualdub-mp3-freeze' , tu selectionnes audio->mP3 audio et zou jpeux pas t'en dire plus a+ |
| Erwan_ | ? |
| Erwan_ |
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| sickBoy73 | dans vdub, menu audio, j'ai 'wav' et 'mp3' .. je choisi
mon vbr et ya pas de pb ... j'ai pas essayé waveMp3 mais je crois que c pas la peine de l'utiliser .. je refait un essai a+ |
| Erwan_ |
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| sickBoy73 | il faut utiliser vitual dub mp3 vbr ... et ya plus de pb !
cherche sur doom9 @+ |
| vink | C'est très simple.
Il te suffit d'utiliser un petit logicile du nom de WaveMp3. Il te permet de faire croire à virtualDub que ton Mp3 est un Wav. Ainsi, tu gagnes du temps en terme de multiplexage. :sol: |
| Erwan_ | C'est pas claire ? :ouch: |
| Erwan_ | Pour gagner un peu de place et ainsi augmenter la qualite d'images de mes divX, j'ai recemment decouvert un nvlle release de VirtualDub qui prends (enfin) en charge une bande son en MP3 Variable.
Un probleme subsiste : VirtualDub necessite "un ficher.Wav" or ma bande son est en "fichier.MP3". Je recupere donc un ch'ti prog (mp32Wav) qui est senser me rajouter l'entete Wav (Riff). A ma grde deception, celui-ci ne semble pas au point. Winamp m'indique que m'a bande son "dure" maintenant 2 ou 3 fois plus longtemps que celle d'origine. (resultat le mixe finale est debile !! env 35fps) Bref, kk1 a-t-il mixe sa video avec du mp3 vbr grace a virtualdub ? Conmment faut-faire? Pourquoi VDub prends pas en charge directos l'extension ".mp3" :hello: Merci d'avance |
