Tag: audio

Micro-review: Bose QuietComfort 15 noise-cancelling headphones

I recently bought these Bose headphones:

qc15_si_lg

Yes, they cost $300. Ouch.

If you travel by airplane more than 1x per year, buy these headphones.

Slightly longer review:

These headphones use active noise cancellation to dramatically slash the volume of loud environments; they work best for continuous, white-noise-like sounds (for example, riding in an airplane). The experience of 4+ hours in the air is completely different when you cut down the noise level. Wearing these, vs. not, is a more dramatic difference in overall unpleasantness, than the difference been first-class and steeragecoach.

Each AAA battery lasts a few flights, sometimes more. You can plug in your media player, computer, etc., or just use the noise cancellation alone.

Become a Better Speaker for $100

The title of this post is a lie. It costs $70 or less, but takes a lot of work. I’ve offered this advice person-to-person many times, and finally got around to posting it.

How well you speak can have a great impact on  your ability to get customers, to attract employees, to persuade others to adopt your ideas, and much more. But how do you know how well you speak? You can’t tell as you are speaking; and if you’ve never heard yourself speak but simply assume you do well, there is a great risk that you are very, very wrong.

To become a better speaker, you need to review your own “performances”. For the last few years I’ve been recording my talks (at user groups etc.) with a hand-held voice recorder. I use an Olympus WS-100 (probably obsolete by now) and you can readily find an adequate device for $70 or less.

Make the Recording

Don’t actually hold the recorder on your hand. Sit it on the podium if you use one (I don’t care for podiums, I use one only if I am presenting with my computer and the podium is the only place to put the computer); but not to close to your noisy computer. Put it on a table or unused chair in the first row, but not too close to any noisy people or equipment.

Start it at the very beginning, and stop it at the very end. It is easy to edit out extra recording later.

Put in a fresh battery, so it doesn’t run out partway through.

Listen to the Recording

Take the recorder/player in your car, copy it to  your iPod, burn to CD, whatever… but listen to it, end to end. Experience your talk as a member of the audience. Make notes about any bad habits you exhibit, such as “umm”, “ahh”, “like”, “ya-know”, long (unintentional) pauses, pointless extra words, etc. This is your first opportunity to become a better speaker by means of the recording. WARNING! The first few times this might be very, very painful.

Edit the Recording

If you plan to post this audio online (as I usually do),  clean up the recording to trim off any extra starting and ending time; the audio you post should start immediately with your talk content and end crisply. Download Audacity (or another audio editing) and use it for this initial trim.

If you can spare the time (approximately 2x the length of the talk), listen through the whole recording in Audacity, trimming out the “umms”, “ahs”, overly long pauses, etc. This is your second opportunity to become a better speaker… but only for the offline listeners, and in an artificial, one-off way. Still, for an occasional important talk it is worthwhile.

Get a Transcript

Finally, be aware that your (now-pristine) audio is completely unsearchable and invisible to Google. To make it findable, have a transcript made and post that also. You can pay CastingWords or other similar service to create a transcript for around a dollar per minute, or perhaps much more cheaply with some searching. The resulting text can be readily posted online, making your talk both more findable, and more accessible.

An example of a recorded, lightly edited, and posted talk (with transcript) is my Ruby GUI talk earlier this year.

Pipe RGB data to ffmpeg

A while back I asked on the ffmpeg mailing list how to pipe RGB data in to ffmpeg. I described it as follows:

in my code I am building video frames, 720x480x24bit. I have in mind generating a large number of these, as long as a full DVD worth at 30fps, then using ffmpeg (followed by dvdauthor) to encode them in to MPEG2 for DVD usage.

There were a few replies, but no definitive answer. With considerable experimentation, I got it to work. It turns out that (as far as I can tell) ffmpeg does not have the ability to accept piped in RGB frames. It will however accept piped in data in its “yuv4mpegpipe” format. With some searching and reading I found that this is roughly akin to the format of raw DV video; each frame consists of a header something like this:

YUV4MPEG2 W%d H%d F%d:%d Ip A0:0 C420mpeg2 XYSCSS=420MPEG2

… then an LF character, then data for the the Y, U, and V “planes”. The Y data is full resolution, while the U and Y are half-resolution (this is called “420” in the video world). These planes are uncompressed, one byte per pixel. All of my past work with computer video (going back to Commodore 64s and Apple IIs) has arranged all of the bits for each pixel within a few bytes of each other; this format (with all the Y data for the whole frame, then all the U data, then all the V data) is starkly different.

The essential problem remaining was how to convert RGB to YUV. Happily there are plenty of online references for this. Unhappily there are few fast implementations, and a naive implementation will be very slow. I solved this problem by finding and hiring an expert in low-level data processing with MMX, SSE2, etc. instructions. (I am not in a position to publish that code here.)

In retrospect, though, there are routines included in Intel’s “Integrated Performance Primitives” library which perform this transformation in a highly optimized way. IPP is a bargain: for only a few hundred dollars you get a wealth of high optimized ready-to-use library routines for signal processing.

The ffmpeg piping solution consists, therefore, of:

  1. A module which generated frames in RGB format, to contain whatever contents your application requires.
  2. A module to very quickly convert these to YUV in yuv4mpegpipe format (write your own, or use routines in IPP, for the RGB->YUV420 part).
  3. Pipe this data stream to ffmpeg with stdin; ffmpeg is invoked something like this: ffmpeg -y -f yuv4mpegpipe -i – -i audio.mp3 -target ntsc-dvd -aspect 4:3 foo.mpg

By using a multicore CPU and threads, this whole process can be made to happen in real time or better (i.e., one second of “wall clock” processing time, for one second of finished MPEG2 video). The resulting MPEG2 file can be used with a DVD authoring application to produce a ready-to-burn DVD ISO image.

Update: the data format above is published here as part of the mjpegtools man pages.

Selling your Software as a Service: Notes and Audio

At the St. Louis Code Camp on May 5, 2007, I gave a talk on Selling Your Software as a Service, in which I discussed our experiences selling a complex (Java) “enterprise” application in that manner. The room was much more crowded than I expected, it was exciting to have an eager group. As with all my recent talks, I used a handout instead of slides. You can download a PDF of the handout (one page, one side), or read the contents below.

The 1 hour audio recording (Olympus WS-100 digital voice recorder, Audacity cleanup) is available here: SAASTalk.mp3

A transcript of the talk is available. In the talk I mentioned Paul Graham’s The Other Road Ahead, which is shorter and easier to read the my talk transcript.

A couple of people at Code Camp asked if I could come give a similar talk in-house at their firms. Yes – please contact me with the contact form to arrange a date.

The handout contents follow.

Continue reading “Selling your Software as a Service: Notes and Audio”

High Quality Screen Recordings

At Oasis Digital we’ve found that we can communicate effectively with each other and with customers, across time and space, using screen + audio recording (also called screencasts or screen videos). We use these to demonstrate a new feature, to explain how code works, to described how a new feature should work, etc. The communication is not as good as a live, in-person meeting/demo, but the advantages often outweigh that factor:

  1. No travel.
  2. No need to syncronize schedules.
  3. The receiving person can view the recording repeatedly, at their convenience.
  4. Customers and develoeprs who join the project team later, can look at old recordings to catch up.

It turns out that I am unusually picky about the quality of such recordings; I’ve written up some technical notes on how to get good results, and posted them: HighQualityScreenRecordings.pdf.

A few highlights:

  • A reasonably fast computer can both run application and record screen video at the same time; but if you will be recording the use of an application that generates a lot of disk activity, you must save the video to separate hard drive (internal, external, network server, etc.) from the hard drive you are running your OS and applications from. (For applications that generate little disk activity, a single system hard drive works fine.)
  • Use a headset-style microphone, and record in a quiet place: close the door, turn off the music, etc.
  • Adjust your audio levels well. Please. This is the most common and most annoying problem with screencast and podcast recordings I find.
  • Bytes are cheap; use a sufficiently large window and sufficiently high bitrate.

Many more details are in the PDF linked above.