Author Archives: Multimedia Mike

VP8 Misplaced Plane

So I’m stubbornly plugging away at my toy VP8 encoder and I managed to produce this gem. See if you can spot the subtle mistake:



The misplaced color plane resulted from using the luma plane stride where it was not appropriate. I fixed that and now chroma planes are wired to use to the same naive prediction algorithm as the luma plane.

Also, I fixed the entropy encoder so that end of block conditions are signaled correctly (instead of my original, suboptimal hack to just encode all zeros). I was disappointed to see that this did not result in a major compression improvement. Then again, I’m using the lowest possible quantization settings for this outing, so perhaps this is to be expected.

Sigh… 4×4 luma prediction is next. Wish me luck.

Gallery of VP8 Encoding Naivete

I’ve been toiling away as a multimedia technology generalist for so long that it’s easy for me to forget that not everyone is as versed in the minutiae of the domain as I am. But I recently experienced what it’s like to be such an outsider when I posted about my toy VP8 encoder, expressing that it’s one of the hardest things I have ever tried to do. I heard from a number of people who do have extensive experience in video encoding, particularly with the H.264 and VP8 codecs. Their reactions were predictable: What’s so hard? Look, you might be a little too immersed in the area to really understand a relative beginner’s perspective.

And to all the people who suggested that I should get the encoder into FFmpeg ASAP: Are you crazy?! Did you see what the first pass of the encoder produced? Do you have lower standards than even I do?



Not Giving Up
I worked a little more on the toy encoder. Remember that the above image is what I’m hoping to encode somewhat faithfully for this experiment. In my first pass, I attempted vertical prediction for all planes. For my next pass, I forced the chroma planes to mid-level (which results in a greyscale image) and played with the 16×16 luma prediction modes. When implementing an extremely naive algorithm to decide which 16×16 prediction mode would be the best for a particular block, this is what the program produced:



For fun, here is what the image encodes to when forcing various prediction modes:
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WebM Cabal

I traveled to a secret clubhouse today to take part in a clandestine meeting to discuss exactly how WebM will rule over all that you see and hear on the web. I can’t really talk about it. But I can show you the cool hat I got:



Yeah, you’re jealous.

The back of the hat has an Easter egg for video codec nerds– the original Duck Corporation logo (On2’s original name):



Former employees of On2 (now Googlers) were well-represented. It was an emotional day of closure as I met the person — the only person to date — who contacted me with a legal threat so many years ago. He still remembered me too.

I met a lot of people involved in creating various Duck and On2 codecs and learned a lot of history and lore behind then– history I hope to be able to document one day.

I’m glad I got that first rough draft of a toy VP8 encoder done in time for the meeting. It was the subject of much mirth.

Announcing the World’s Worst VP8 Encoder

I wanted to see if I could write an extremely basic VP8 encoder. It turned out to be one of the hardest endeavors I have ever attempted (and arguably one of the least successful).

Results
I started with the Big Buck Bunny title image:



And this is the best encoding that this experiment could yield:



Squint hard enough and you can totally make out the logo. Pretty silly effort, I know. It should also be noted that the resultant .webm file holding that single 400×225 image was 191324 bytes. When FFmpeg decoded it to a PNG, it was only 187200 bytes.

The Story
Remember my post about a naive SVQ1 encoder? Long story short, I set out to do the same thing with VP8. (I wanted to do the same thing with VP3/Theora for years. But take a good look at what it would entail to create even the most basic bitstream. As involved as VP8 may be, its bitstream is absolutely trivial compared to VP3/Theora.)
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