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Improving the Quality of Your Flash Video and Audio Output in Flix
Contents
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Introduction
There are many factors involved in creating a good looking and sounding Flix swf video file. This tutorial covers the range of issues involved and makes many suggestions on how to get the best quality video. Because of the nature of digital video and audio compression, you will need to experiment in order to find the settings and methods that work best for you on a case-by-case basis. Some of the issues covered here relate only to Flix's Flash 3-6 output. Flix's MX/FLV output is over 300% better than the Flash 3-6 output, and you can instantly improve your quality by selecting the MX output (please note that Flix's MX output will only play in the Flash 6 player). However, many of the issues discussed - especially those that relate to creating your source video - apply to all Flix outputs.
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Your Source Video
The single most important factor in making your Flix encoded videos look good is to start with a good source file. So the capture process is extremely important. The better your source looks, the better your Flix encoded video will look.
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Capturing Your Video
There are many capture cards available on the market. Some provide markedly better quality than others. We use an Osprey capture card (www.viewcast.com) with audio and video inputs. Though the Osprey card costs less than many other cards, we have found the quality to be quite good. Additionally, we recommend using a capture card with both audio and video inputs to help keep the video and audio in sync.

You should capture your video using a codec that incorporates some level of compression.
Video Compression
While Flix can encode uncompressed video files, it creates better looking swf video files from video sources with some compression. We recommend using AVIs with one of the well known compression codecs (Indeo, Cinepak, etc.) or MOV (Sorenson). However, you should avoid using the windows media codecs, .wmv and .asf. While Flix can convert those files, it does not yield the highest quality. You should be aware that compression reduces the size of different images based on many factors, including motion, brightness, contrast, color hue, etc. so there are no absolute rules.

Use the capture video image controls with your capture software to adjust the appearance of your video carefully.
Video capture
Most capture cards provide image controls such as color saturation, hue, brightness, and contrast, and you should play with the settings to make your video look the best it can. If there are particular sequences in your video that are too dark, or light, or the color is wrong, you should recapture those sequences and edit them into your video. Rarely does a single capture setting work across a long stretch of video. We also suggest making your capture files a little on the brighter side, as this will convert better later.

When you capture, use a high bitrate setting, a high frame rate, and a large image size. You should capture a source video file that has the largest image size, frame rate and bitrate, that you will ever want the video to be - through subsequent generations of conversions.
MPEG-4 Video Codec
Capture video sequence
The bitrate is a measurement of the amount of digital information that will be encoded into your video in relation to the duration of the video clip (bits per second). The higher your bitrate, the better your video will look and the more memory it will take up. Your subsequent encoding with Flix will never look better than your original. So start with the best quality original you can. For web video, we recommend creating a source of 320x240, with a framerate of 30 fps and a bitrate of 3 mbps. The standard video framerates are 30 fps for NTSC video (US standard) and 25 fps for PAL video (European standard). Film is usually shot at 24 fps, which is converted to 30 fps or 25 fps when it is transferred to video. It is always best to match the original framerate for capture. So if your source was shot at 25 fps, you should match that speed. You may later create conversions with a different framerate, but it is best to maintain the original framerate as long as possible.

You will also want to capture your video with the same aspect ratio as your source. The aspect ratio is the ratio of the width to the height of your video, as measured in pixels. So if the ratio of width to height is different in your captured video, than the ratio of your source video, you can get an image that is distorted. If you do not want this type of distortion make sure your capture image dimension settings have the same ratio as the capture source (in this case, the ratio is what is important - not the size).
Aspect ratio
If your capture source is in letterboxed format (with black bars at the top and bottom), try to use a capture software that allows cropping so you can remove the black bars. These black bars take up memory and will also take up memory when you convert your files into swf with Flix. If you eliminate the black bars the memory they would have taken up will be applied to the rest of your video - the image portion.
Custom size
When capturing use the best computer you have access to. Make sure your capture software works well with your computer's operating system and hardware/software configuration. Sometimes the OS/hardware/software on your computer can conflict with video capture, encoding and editing software. You will also need a lot of processing power, RAM and hard drive space to store your video files. We strongly suggest you do not multi-task while capturing your video.

To reiterate, the quality of your source video is the single most important factor in determining how your Flix encoded video will look. So take the time to get the best quality you can.
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Your Flix Settings
As a guideline, we suggest that you start with the presets in Flix (File tab) and then adjust your various settings until you find what you are looking for.

Always try to use a source video file that is at least the same image size, frame rate and bitrate, or preferably larger, than the one you are creating. The key settings and factors to consider are:
  • Video size (Video tab). If you reduce your video size (image dimensions), your picture will be sharper. Another small factor you may consider is that optimal frame sizes are divisible by 8. That means that if your image dimensions (width and height) are divisible by 8, you will be wasting as few bits as possible on encoding data for portions of the video which do not actually appear. This is a complex issue relating to the way image compression uses 16x16 and 8x8 blocks to form an image.
  • Video Framerate (Video tab). If you decrease your video framerate (which is different from your SWF framerate), your picture will be sharper - but the video will appear choppier during playback.
  • Video Framerate Compatibility (Video tab). You may need to make sure that the video framerate you select is a factor of the framerate of your source video file. For instance, if the video you are encoding from - your source - was encoded at 15 fps and you are using 6 fps video, 6 does not divide evenly into 15 and it may cause a conflict that results in reduced video quality. This is especially important for MX video output.
  • Maximum Bitrate (Video tab). If you increase the maximum bitrate you select, your image quality will improve. Remember that if you are creating video for the web, the maximum bitrate setting determines the speed of the internet connection required to view the video if it is being streamed - as opposed to using a pre-loader. You may also deselect the maximum bitrate (so there is no maximum bitrate at all). This should only be used with Flash 3-6 output and for CD-ROM and other local applications. Note: If you are using the MX video output if you deselect the maximum bitrate option, your video will be encoded at a constant quality with the quality setting you have selected in the Video tab. With MX video you will get a better result using a bitrate than without.
  • 2-pass VBR. If you are exporting MX video you will achieve your highest quality using the 2-pass VBR output.
  • Image filters. You can use the image filters in the Edit, Crop and Filters window to improve the appearance of your video. Probably the two filters that can improve your quality the most are deinterlacing and noise reduction.
    • Deinterlace video: Selecting the "Deinterlace video" option will automatically remove the image distortions caused by interlacing. Interlaced video frames can often appear to have various image distortions, such as comb-like effects, alternating lines, or striping. This is especially relevant for high action scenes and larger, full-screen video images.
    • Noise Reduce: This feature can be used to compensate for some of the pixelation characteristic of digital video compression. This feature can also be useful at lower image quality percentages (when pixelation increases) or if you apply custom "SWF" dimensions and stretch your image
    Flix also has 4 color filters that affect the appearance of your video. These work best to make minor modifications to your output, or to create a specific look.
    • Bright: Adjusting the brightness makes the image lighter or darker.
    • Contrast: Adjusting the Contrast changes the range of dark to light pixels in a linear fashion.
    • Hue: Adjusting the hue will change the overall property of the colors in your video.
    • Saturation: Adjusting the saturation (which is sometimes called chroma) alters the strength or purity of the colors in your video.
  • Average Image Quality (Video tab). You can increase the average image quality. This applies if you have not selected a "maximum bitrate," which will reduce your image quality to fit within the limits of the maximum bitrate you have selected. This is most relevant to the creation of using Flash 3-6 video for CD-ROM where the bandwidth of the video is not an issue. The average image quality setting operates on a logarithmic scale. This means that as the numbers get towards the end of the scale - i.e., 100 - the actual value increases dramatically, while perceived quality does not increase dramatically. Consequently, we recommend not increasing this setting above 80-85.
  • Video Codec. The codec of your source video (which is listed in the Input Video Properties box of your Video tab) may not be 100% supported by Flix and Flix may have a problem with it, even though it encodes. You can try re-encoding your source video to a different codec and see if that improves the quality. There are many different programs that will convert video from one format to another.
Input video properties
  • Preloaders: you can use a pre-loader to provide viewers on a lower bandwidth connection, with a higher bandwidth video, though it will not start playing immediately. Preloaders load a predetermined amount of a video file before the video starts to play. In addition, in the SWF Tab of Flix there is an option to add an automatic preloading function to your Flix output.
  • Custom SWF Dimensions (Video tab). You can use the custom "SWF" dimensions setting to increase the image size of your output video without increasing the file size. However, as the image size increases, the image will become more pixelated. You can compensate for some of this pixelation by selecting "Noise Reduce" filter (in the Edit, Crop and Filters Window).
  • Maintain Aspect Ratio. Flix allows you to set any image dimensions you desire for your output swf video, and the presets include specific image dimensions that will be applied to your video regardless of the size of the source video. However, if you change the aspect ratio of your video, the output may appear distorted. The aspect ratio is the ratio of the width to the height of your video, as measured in pixels. So if the ratio of width to height is different in your Flix output settings, than the ratio of your source video, you can get an image that is distorted. If you do not want this type of distortion make sure your Flix output image dimension settings have the same ratio as the source (in this case, the ratio is what is important - not the size). Flix will do this automatically if you set "Maintain aspect ratios" in the Video Tab.
  • Editing and Cropping. You can use the editing and cropping features in Flix Pro to remove unwanted material from what is encoded. In this way the amount of encoded data is significantly reduced and more encoding bits can be applied to the selected material of interest, which improves quality.
  • Audio Bitrate (Audio tab). If you decrease the audio bitrate the extra bits will automatically be applied to your video.
Output audio options
  • Audio Export (File tab). If you do not export audio with your video, the extra bits will automatically be applied to your video.
Audio selected:
Export options
Audio deslected:
When encoding your video with Flix use the best computer you have access to. You will need a lot of processing power, RAM and hard drive space to store your video files. We strongly suggest you do not multi-task while capturing your video.
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Audio Quality
As with the image quality, the single most important factor in making your Flix encoded videos sound good is to start with a good source file. So the capture process is extremely important. The better your source sounds, the better your Flix encoded video will sound.

Capture your audio with the highest sampling rate and bitrate possible.
Sound selection
The sampling rate is the frequency, or the number of samples per second, at which the audio is encoded. This is measured in Hertz (Hz). The bitrate value determines the amount of information used to store the audio in your video file. This is measured in kilobits (1000 bits = 125 bytes) per second (Kbps). Higher bitrates lead to higher quality audio and larger file sizes. As a point of reference, the audio on a music CD is an uncompressed WAV file encoded at 44.1 kHz, 16 bit stereo (with a bitrate of 172 kbps). We recommend capturing to uncompressed PCM audio at 44.1 kHz, 16 bit. Use stereo if your source is stereo and mono if your source is mono. You can also use any of the other high quality audio codecs (such as Qdesign for MOVs).

In general, it does not matter whether your source is stereo or mono as long as the sound quality is high (unless, of course, you are trying to create a stereo effect). Some audio codecs, such as mp3, use special algorithms to create stereo sound, and when converted using Flix can result in unusual audio effects, especially at lower bitrates.

Your encoding with Flix will never sound better than your original. So start with the best quality original you can. When using Flix, always use a source file in which the audio has at least the same sampling rate and bitrate (or preferably higher) than the one you are creating. Also, if you want a stereo output from Flix, your source video should have stereo audio.

When capturing use the best computer you have access to. You will need a lot of processing power, RAM and hard drive space to store your files. Do not multi-task while capturing your audio.
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Your Flix Settings for Audio
  • Output Audio Options (Audio tab). Flix uses the MP3 format to encode audio. This is the audio codec used in the swf format. It results in good quality audio at fairly small file sizes. The lowest audio setting in Flix is 11 kHz and 8 kbps. This results in a small file size, but the quality is not that great. By increasing your settings to at least 22 kHz and 16 kbps, your audio quality will greatly improve. By increasing the bitrate you will continue to increase the quality of your audio, but you will also increase the file size, or, if you have selected a maximum bitrate, you will increase the bits allotted to the audio portion of your video at the expense of the image portion of your video. 128 Kbps MP3 audio is generally considered to be equivalent to CD quality audio and results in file sizes that are 10% the size of the uncompressed WAV files actually used on a music CD.
Output audio options
  • Stereo (Audio tab). Flix uses the stereo feature in MP3 audio. Using stereo will not increase file sizes. However, we recommend using stereo with minimum audio settings of 22 kHz and 40 kbps. You will get better quality at lower audio bitrates with mono.
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Audio Sync
A major issue in digital video is keeping the audio in sync. In general Flix maintains excellent audio sync. However, if you are experiencing sync problems, there are a number of issues to consider. Below are just a few.

To start it may be helpful to explain a couple of things:
  1. Flash video has two framerates:
    1. a video framerate, which is the number of distinct video frames per second in your video
    2. a SWF framerate, which is the number of SWF frames in your final Flash video. These are not the same thing and you have to keep track of both - and how they relate to each other and to the source video framerate. Flash video is different in this way then standard video which has only a single video framerate.
  2. A factor is a mathematical term that describes one of two or more quantities that divides a given quantity without a remainder. For example 1, 2, 3 and 6 are factors of 6; 1, 2, 3, 5, 6, 10, 15, and 30 are factors of 30, and so on. Potential reasons for loss of audio sync:
    • The video framerate of your output SWF conflicts with the video framerate of your source video. The video framerate of your SWF video should be a factor of your source video framerate.
    • The SWF framerate of your output SWF conflicts with the video framerate. The SWF framerate of your SWF video should be equal to or a multiple of your video framerate.
    • The video SWF file created uses up too much RAM for the system it is running on, resulting in a loss of sync.
    • The SWF file that the video is embedded (or loaded) in uses up too much processor power for the system it is running on, resulting in a loss of sync.
    • The source has errors, which cause loss of sync.
    • The source codec used is not 100% supported.
    • The computer used to encode lacks the processing power and/or ram required to encode with sync.
    • There may be a conflict between the audio settings you are using (frequency and bitrate) and the audio settings of your source video. You can try to experiment by altering your settings to see if it helps the problem. Often, increasing the frequency and bitrate can solve this problem.
    • The video framerate being used is very low and the resulting video appears to have audio and video out of sync (especially with talking mouths) but in fact it is in sync and the appearance of sync loss is caused by the very low frame rate.
    • The audio and video of the source video was captured with separate cards which results in a loss of sync that gets worse with subsequent generations. We recommend using a capture card with both audio and video inputs to help keep the video and audio in sync. We use an Osprey capture card with audio and video inputs. Though the Osprey card is less than many other cards, we have found the quality to be superior.
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Wildform's Sample Videos
Many people ask how we made the videos in the video jukebox on our homepage. Those Flix encoded swfs were made from Mpeg-4v2 AVIs encoded from a VHS tape - so nothing special. We did make sure to get a good looking capture file. The audio was captured with uncompressed PCM audio at 44.1 kHz, 16 bit stereo (from a stereo source). We used an Osprey capture card with both audio and video inputs (which helps keep the video and audio in sync). Though the Osprey card is less than many other cards, we found the quality to be quite good. Then we used the presets in Flix to encode, with some minor tweaking.
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Conclusion
There are many factors involved in creating high quality digital video with Flix. This tutorial has covered some of them. Digital video and audio compression varies depending on the nature of the source material. So the key to finding what works best for a particular clip is to experiment. The more you work with video the more you learn about how different video/audio will be affected by compression and the easier it gets to make a good looking and sounding video. This tutorial is intended to get you started in the right direction. Happy encoding.
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