Streamclip 1.9.1 - some advice needed please

[shoosh]

Hi, I have a documentary movie, originally split into 2 avi's, which Streamclip has joined together perfectly, however I can't seem to get the audio settings right. I'd like to keep the original audio (AC3) rather than converting to mp3 - Streamclip Help mentions choosing "pass through" if you intend to leave the original audio unaltered, but under the audio pull-down menu there's no pass through option listed, so I've been forced to convert. Is "pass through" an option which only appears in the audio menu in certain circumstances? Seems odd that it should be mentioned in the Help but not appear in the menu. Is the "uncompressed" option the same thing as pass through? Sorry, I'm new to all this and it's a bit confusing.

The other thing that's a bit weird is the bitrate settings. The original has a bitrate of 1599.56 kbps and a 1.36GB file size, but when converted using the limit bitrate option (to 1599 kbps), it actually converts to 1655 kbps and a 1.4GB file size. Shouldn't the two be the same?

One last thing, a general newbie question: is XviD a better quality codec than DivX, and will XviD avi's play ok on a DivX dvd player?

Thanks.

[tomlee59]

You may want to try the file joining tool in D-Vision 3: http://www.objectifmac.com/dvision.php At least it's free, so if it doesn't work, you won't feel too chapped.

As to your other questions, here are some brief partial answers: "Uncompressed" and "pass-through" are different things. The former generally refers to pure pcm (e.g., .wav or .aiff, or .pcm, for that matter). If the audio isn't already in one of these formats, then a re-encoding step will take place to produce them. Passthrough means that no re-encoding of any kind ever takes place.

As to bitrate discrepancies, there are a couple of possibilities. For one, the bitrate settings in an encoder are generally a target (or, in some software, a maximum value). Depending on the detailed nature of the source material, the target may or may not be achieved with great accuracy. What's very confusing is that "constant bitrate" encoding doesn't always mean what it says (for video; it always does for audio). An additional confusion can be the differing ways of reporting binary numbers in decimal format. A kilobit can be 1000 bits, or it can be 1024 bits. Similarly, a megabit could be 1000 or 1024 kilobits, etc. The software you use to read the data rate of a movie could be using one standard, while the software you use to encode the movie could be using the other. The difference -- 2.4% in this case -- seems to be about what you're seeing, so that is a likely possibility here.

As to XviD v. DivX, they are not greatly different in quality, but to my eyes, XviD produces marginally better results. As for whether a standalone player will handle both, that is very much a function of the player; there is no guarantee. XviD and DivX are similar enough that a manufacturer could support both with minimal effort, but that does not mean that the manufacturer will exert that minimal effort. DivX is simply not widely supported among standalone players, so you'll have to experiment (or read their documentation) to see what formats a given player will actually play. Generally, support is only for a limited set of codecs, and for a limited range of datarates, frame sizes, etc.


HTH some.

[shoosh]

Thanks for your reply, Tom. That's explained mostly everything - I'm still unsure why Streamclip's sound menu doesn't include the pass-through option mentioned in the Help section, but I guess I can live with the audio in mp3 instead. I'll try sending an email to the developer to see if he can help. Thanks a lot for taking the time to reply, I appreciate it.

[usually_quiet]

Mpeg Streamclip is primarily an editor for MPEG-1 or MPEG-2 video, hence the name. As a bonus, the authors allowed some other types of video files as input, but intentionally restricted the available output options for them.

Unfortunately it appears that a certain number of people are now using it primarily for its bonus features, without being aware that there are restrictions placed on on them. One needs to read the "Requirements" and "Features Description" sections on the authors'own download page very carefully to find out what is possible, and reading the users guide is sometimes necessary as well.

Even so, I could not determine with certainty whether not passing through AC3 sound for imported AVI is a bug, or an intentional restriction. On one hand the documentation says that AC3 sound is permitted when exporting to AVI, but on the other hand all the information provided about the "passthrough" option refers to MPEG-1/MPEG-2 sources. It's definitely available if you start with MPEG-2 video and AC3 audio and want to export to AVI. Based on that, it seems more likely not making the passthrough option available if one is editing an AVI file is deliberate decision, but I guess only the authors know for certain.

[tomlee59]

Usually_quiet has a good point, which is one additional motivation for trying out D-Vision 3. Its avi joining tool does no re-encoding of any kind. So the output and input formats will be the same. Assuming that this is the result you are seeking, then perhaps it's worth a go. As I said before, it's free and fast, so you will waste little in the attempt, even if it ultimately fails.

[shoosh]

Thanks for the help, guys. Just have one more thing to do - is there any way I can crop the .avi without re-encoding? I've tried with Streamclip, D-Vision 3 and ffmpegX, and haven't had any luck. Looks like cropping is only available as part of the encoding process, and if I do that I end up with either different audio, a different codec or larger file size. Can't seem to win! Any suggestions?

[tomlee59]

Alas, cropping requires re-encoding. If you change the image, you change how it's represented. That means it will need re-encoding. If the standards had been written to allow a user-defined border, for example, things would be different. Regrettably, that's not how it's evolved.

[shoosh]

Ok, thanks Tom. I'll just settle for things the way they are then. Might try re-encoding if it looks too distracting on a large screen, but otherwise I'll leave it. Many thanks for your help and patience. Cheers.