FLV Preset Customization

Last Updated: Apr 25, 2014 01:14PM PDT
Flash video (FLV) was at one time the most popular video format on the internet. The Flash 8 (F8) presets in Squeeze use the On2 VP6 codec which is more advanced than the Spark codec used in F6 FLV presets and will give you more optimal results every time when compared to Spark Flash 6 presets.

On versions of Squeeze earlier than 6, the VP6 codec was only available by purchasing Squeeze Pro or by purchasing the codec separately as a plugin. If you have squeeze 5 or earlier you can contact the Sales team to purchase the plug-in - sales@sorensonmedia.com

Below you can see an example of the settings of F8 480p (16x9) preset. This preset has a high quality standard definition output and is a great preset to use for your online videos.



Video Check-box
Includes video in the preset. If this is unselected, the video options cannot be changed, and the preset will export audio only, according to the audio settings.

Codec
A video codec is the software application that compresses the video portion of your movie. Sorenson Spark Pro and On2 VP6 Pro are the video codec options for Adobe Flash (.flv). As mentioned above, On2 VP6 is recommended for all desktop use.

Method
Allows you to select from the available compression methods. Sorenson 1Pass VBR, Sorenson 2-Pass VBR, or 1- Pass CBR, are the options for Adobe Flash (.flv).
Variable bit rate (VBR) method varies the amount of output data per time segment. VBR allows a higher bit rate to the more complex segments of media files while a lower data rate is allocated to less complex segments (i.e. talking-heads or Power Point presentations). This keeps the quality consistent while keeping file size low.

With VBR, you have the option of 1 pass, or 2 pass. Multiple passes will provide superior output quality, but will also multiply the amount of time it takes to complete the encoding job.

Constant bit rate (CBR) keeps a consistent bit rate throughout the duration of the file. This can be helpful when using a streaming server that needs a constant bit rate stream. Because the bit rate is consistent regardless of complexity of video content CBR encoded files usually need a higher data rate and produce larger file sizes than files using the VBR method.
Frame Rate: Frames/Sec.
Indicates the number of frames (individual pictures of the movie) that are played each second. The higher you set the Frame Rate, the smoother the playback appears. The default frame rate is 1:1, which means if the source file is 30fps (frames per second), the output will be 30fps as well. This is the optimal setting unless your source file is greater than 30fps, in which case you will want to specify the Frame Rate.

Data Rates
Data Rate (bit rate) is the single greatest determining factor of the quality and size of the output video file. Select the Preset Data Rate that meets the needs of your audience. The greater the data rate, the higher quality the output, but larger the resources -both on the local machine and the network -will be required to play back the file.
To finish explaining the Simple settings first, we will move over to the right column.

Frame Size
This specifies the width and height and aspect ratio policy of your movie. There are four choices of aspect ratio policy found in the Frame Size section:
Same As Source: This will output files with the same frame size as the source file. When this is selected, the Frame Size fields will become inactive.
Unconstrained: Allows you to freely change the width and height of the video at the expense of the aspect ratio. If the aspect ratio between the source and the output is different, then the video will be squished or stretched to comply with the newly entered settings.
Maintain Aspect Ratio: Constrains the video, so if you enter the width, the height is populated automatically, or vice versa. By default, the Maintain Aspect Ratio option is selected.
Letter Box or Pillar: Maintains the original size of the video and places black bars on the side of the video for pillar and on the top for letter box if the aspect ratio is different between the source frame size and the output frame size.
Note: Only even numbered dimensions are allowed for the frame size

Key Frames
In video compression, a key frame, also known as an Intra Frame, is a frame in which a complete image is stored in the data stream. Only changes that occur from one frame to the next are stored in the data stream. This reduces the file size without a reduction in visual quality. This technique capitalizes on the fact that most video sources (such as a typical movie) have only small changes in the image from one frame to the next. Whenever a drastic change to the image occurs, such as when switching from one camera shot to another or at a scene change, a key frame helps to keep the quality high.
“Key Frame Every” will allow you change the maximum number of frames that are allowed between key frames. You can change the frames according to “key frames per second” or “key frames per number of overall frames”.

In “key frames per number of overall frames” you can choose between 1 and 500 frames. In more complex video with fast action this option should be set to a lower value to allow more key frames because of the potentially large changes between each frame.
Clicking the Advanced button when the video codec On2 VP6 Pro is selected expands the dialog box further to provide options for advanced users. These features give you great looking digital video, even at very low data rates. We will go back to the Left column and work our way down.



Compress Alpha Data
Selecting the Compress Alpha Data setting compresses alpha channels. This is the only preset in Sorenson Squeeze that allows for alpha data preservation. To preserve your alpha channel, check this box. *note: This feature only works with .MOV source files with alpha channel. AVI files with alpha channels will not work.
Alpha Data Rate: The percentage of the target data rate allocated to the compression of alpha data. The YUV data is allocated a percentage of the target data rate equal to 100 – Alpha Data Rate.
Auto Key Frames Enabled
If this option is selected, the encoder determines where to place keyframes in the output (i.e., a static keyframe interval is not used).
Auto Key Frame Threshold: Determines the frequency of keyframes. If two frames are drastically different, the encoder inserts a keyframe. This threshold determines how different the frames have to be before a keyframe is thrown. A higher number means fewer keyframes.
Minimum Distance to Key Frame: This will change thse size of the interval between keyframes. The minimum number of frames that are allowed between keyframes. Setting this option to a very low value may cause an increase in the average data rate of the output.
Compression Speed
Allows you to speed up the encoding process.
Best - Produces the best results but takes the longest to run.
Good - Produces good results and runs fast but does not worry about running in real time.

Speed Slider
Determines the speed at which the compressor attempts to compress the frames it gets if Compression Speed is set to Fastest. The speed slider is locked to 12 on version 7 of Squeeze.
Minimum Quality -Worst allowed frame quality (lower is worse). A high number ensures a frame will not appear poorly but it may hamper the compressor’s ability to hit the data rate you requested without dropping frames.
Maximum Quality - The best allowed frame quality. Higher is generally better.
Quality - Uses a constant frame quality as specified by the value in quality. Higher is generally better. Data rate control is only achieved by dropping and/or resizing the frames if they are enabled.
VBR Variability
Determines the amount of variability if VBR is selected. A value of zero creates a constant Bit Rate output (CBR), and a value of 100 creates a highly variable bit-rate file, proportional to difficulty of the section that is being encoded. The decision as to where to put the slider will coincide with the same principles of whether or not to choose Constant or Variable bit rate in the first place.

Drop Frames To Maintain Data Rate
Allows the compressor to drop frames in order to hit a specific data rate. In particularly difficult portions of the file, the encoder will drop frames to achieve the target data rate.

Drop Frames Watermark
Determines the percentage of the data rate buffer below which the encoder is enabled to start dropping frames. This does not refer to Watermark Filters, rather it is referring to the “high mark” or “water mark”. Think of it as the “Drop Frames Threshold”.

Sharpness
Controls the sharpness of the image in the output. This setting does not impact any other setting and is largely a matter of personal preference. A low sharpness setting will result in fewer visible artifacts but may blur the image somewhat; a high sharpness will result in a sharper image but may result in more visible artifacts. The lowest sharpness setting is 0, and the highest is 10.

Noise Pre-processing Level
The level of video noise filtering to apply. A level of 0 is no pre- processing, 6 is highest level of temporal pre-processing.

Starting Buffer Level (only applies to the CBR Method)
The number of seconds of data that are preloaded by the media player before playback. The buffer is used to maintain a consistent data rate and minimize playback interruption.

Note: The buffer level is not a delay playback control. The buffer is how much of the video is being stored on the viewers machine.

Optimal Buffer Level (only applies to the CBR Method)
The buffer size, in seconds, that the encoder strives to reach or maintain in case of specific frame overshoots.

Maximum Buffer Size (only applies to the CBR Method)
The maximum size of the buffer, in seconds. Output that will be streamed using a TrueCast Server, the maximum buffer size is 6 seconds.

Minimum 2 Pass VBR Data Rate (only applies to 2 Pass VBR)
The lowest data rate (a percentage of the target data rate) that the encoder will allow for any section, no matter how easy the section is. This value is used to prevent difficult sections from stealing too many bits from easy sections. The default is set to %40

Maximum 2 Pass VBR Data Rate (only applies to 2 Pass VBR)
The highest data rate (a percentage of the target data rate) that can be streamed, and also the highest data rate that the encoder will allow, no matter how difficult the section is. The default is 400% which may be a bit high. Other codecs have a VBR max data rate of around 150% and we recommend reducing the maximum data rate closer to 150% or lower to be closer to the target data rate.

Data Rate Undershoot
This creates an output that targets a slightly lower data rate (a percentage of the target data rate) so bits are available in the buffer to improve more complex portions. The default is 100% which means that it won’t do any undershooting unless you move the slider down.
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