SWF

These are probably the most important tags in this reference. They are used to define a shape using Bezier curves and lines with different styles. The DefineShape of V1.0 is usually enough unless you need a large number of styles or you want to specify colors with an alpha channel (RGBA).

The DefineMorphShape and DefineMorphShape2 can be used to render an intermediate shape between two defined shapes. All the points and control points of both shapes must match. This is because the rendering of the morphing shapes is just an interpolation between both shapes points and control points positions. The interpolation is a very simple linear function (note however that you still can use a non-linear transformation effect in the end.) Most of the parameters in a shape definition are doubled when this tag is used. It otherwise looks very similar.

The f_stroke_rect and f_stroke_rect_morph rectangles define the boundaries around their respective shapes without the line strokes (excluding the thickness of the line.)

The f_define_shape_non_scaling_strokes flag should be set to 1 if at least one of the line strokes always stays the same while morphing.

The f_define_shape_scaling_strokes flag should be set to 1 if at least one of the line strokes is changing while morphing.

The f_offset_morph 32 bits value gives the offset from after that value to the start of the second shape (the shape to morph to.) In other words, this value can be used to skip the styles and the first shape at once.

The SoundStreamHead[2] tags define a sound effect which is to be loaded with a set of SoundStreamBlock tags. It defines the sound once and for all.

Streaming sound has a strong side effect when playing a movie: it will force a synchronization between the images and the audio. Thus some images may be dropped if the drawing isn't fast enough.

Streaming sound effects should be either used in the main movie or in a sprite which needs a sound track properly synchronized to the sprite animation. Otherwise, it is much better to use the DefineSound and StartSound tags.

It seems (though it isn't documented) that using a SoundStreamHead tag by itself (without any sound blocks) is taken as a hint of how to play all the other sounds in an animation (see the f_playback_rate)

Important note: there can be only one streaming sound per movie clip including the main movie. If you need multiple sound effects or music to be played back, these will have to be merged at the time you create the movie in a single sound which will then be played back as a single sound track.

Some of the fields in the SoundStreamHead tag can't have all the possible values when defined in an older version of SWF. What follows describes each field in more details.

The f_playback_rate and f_sound_rate define the rate at which the data should be played and the exact rate of the data found in the SWF file.

	rate = 5512.5 * 2 ** f_playback_rate
	rate = 5512.5 * 2 ** f_sound_rate

The f_playback_size and f_sound_size define the number of bits found in the data (0 for 8 bits and 1 for 16 bits.) Note that with a SoundStreamHead tag (18) only 16 bits data are allowed (both are always set to 1). If the compression mode isn't Raw or Uncompressed then the f_sound_size must be set to 1.

The f_playback_stereo and f_sound_stereo define whether the sound should be played on both speakers and whether the data includes both channels.

The f_compression entry defines the compression mode. The list of sound compression modes can be found with the DefineSound tag. Note that with a SoundStreamHead tag (18) only the ADPCM compression is accepted. All the compression modes are accepted in a SoundStreamHead2 tag (45).

The f_sample_size represents the average number of samples per frame. It is used to ensure a proper synchronization. Note that there can be more (and even less in MP3) samples within a given frame.

The f_latency_seek is usually zero. It exists only when the MP3 compression mode is used. It defines the number of samples to skip at the beginning of the very first frame (I'm not totally sure what this is to tell you the truth... I'll tell you more once I know more).

These tags declares a loss-less image bitmap. It has a small header followed by an optional colormap and the bitmap data. When we have a colormap, the bitmap data is an array of indices in the colormap aligned to 4 bytes on a per row basis.

There are three supported formats:

Format No. (bits)	Color Format		Comments
	Without Alpha	With Alpha
3 (8 bits(1))	RGB	RGBA	Uses a colormap with up to 256 entries of 24 or 32 bits colors.
4 (16 bits(1))	RGB555	RGB555	There is no alpha available in this format. The data is saved in big endian (it is NOT a U16 like some documentations say it is). The colors looks like this (most significant bit first): 0RRRRRGGGGGBBBBB. You should certainly always use the DefineBitsLossless tag for this format.
5 (32 bits)	XRGB	ARGB	Uses a strange order for the components. Most probably because the alpha was added later and thus inserted in place of the X to keep some backward compatibility with older versions.

⁽¹⁾ the data must be 32 bits aligned (4 bytes) on a per row basis. In 8 bits, you may have to add up to three bytes at the end of each row ( 4 - width & 3 when width & 3 is not zero.). In 16 bits, you need to add two bytes at the end of each row when the width of the image is odd.

The f_colormap, f_indices and f_bitmap are all compressed with the ZLIB scheme.

WATCH OUT: the f_colormap and f_indices are compressed as one large block.

WARNING: These tags require you to save the swf_tag in long format (i.e. f_tag_and_size & 0x3F == 0x3F even if the size is smaller than 63.)

WARNING: An image cannot always be scaled more than 64×. Trying to enlarge it more may result in a rectangle of one color. The 64× is cumulative. So a sprite of an image × 3 inside another sprite × 10 inside another sprite × 4 results in scaling of 120 and this is likely to break the image. This seems to be true mainly when there is a rotation or skew.

These tags define an image saved using the JPEG compression scheme.

DefineBitsJPEG (V1.0) does not include the encoding tables which are defined in the unique JPEGTables tag instead. All the DefineBitsJPEG of an SWF file use the only JPEGTables tag. Yes... This means you need a tool that is capable of reusing the same tables over and over again to make sure that all your DefineBitsJPEGs work properly (or use it just once.)

The other tags incorporate their own version of the JPEG encoding tables.

The DefineBitsJPEG3 and DefineBitsJPEG4 support an alpha channel bit plane (8 bits.) This alpha channel is compressed using the ZLIB scheme as defined with the DefineBitsLossless image formats and appears at the end.

With Flash 10, DefineBitsJPEG4 was introduced to support a deblocking filter parameter. This parameter should be set to a value between 0.0 and 1.0 (0x0000 and 0x0100--so really a value from 0 to 256 inclusive.)

WARNING: These tags require you to save the swf_tag in long format (i.e. f_tag_and_size & 0x3F == 0x3F even if the size is smaller.)

f_encoding should include 0xFF 0xDB and 0xFF 0xC4 entries.

The f_image_data buffer should include the 0xFF 0xE0, 0xFF 0xC0 and 0xFF 0xDA.

Since Flash 10 the f_encoding and f_image_data fields defined in the DefineBitsJPEG2, DefineBitsJPEG3 and DefineBitsJPEG4 tags, are viewed as one single large buffer and thus it can be a verbatim JPEG, PNG or GIF89a file.

When the buffer represents a JPEG, it starts with 0xFF 0xD8 and ends with 0xFF 0xD9.

When the buffer represents a PNG, it starts with 0x89 0x50 'P' 0x4E 'N' 0x47 'G' 0x0D '\r' 0x0A '\n' 0x1A '^Z' 0x0A '\n'.

When the buffer represents a GIF89a, it starts with 0x47 'G' 0x49 'I' 0x46 'F' 0x38 '8' 0x39 '9' 0x61 'a'.

The f_alpha buffer is compressed with ZLIB as defined in the DefineBitsLossless tag (this is similar to the PNG format). WARNING: this field only works with JPEG data. A PNG or GIF89a cannot make use of this field (but they can make use of their own alpha channel.)

The DefineBitsJPEG tag may fail if it includes any encoding tables. These tables shall be defined within the JPEGTables instead.

Note that the Adobe SWF player better enforces the correctness of these tags since version 8. Some older movies may not work properly with Flash Player 8+.