<!—#set var="article_header" value="MPEG-4 With The New Flask 4.1:
Almost DVD Quality» —>
The New Flask 4.1/DivX 4.01 Codec
New Flask 4.1, designated Xmpeg 4.1.
Encoding MPEG-4-Videos has become a cult. All over the world, hundreds of thousands of users are turning DVD movies into the space-saving MPEG-4 format so that they can then burn them onto one or two CD-Rs. Countless Internet forums share tips on optimizing the settings, with the sole objective of getting the best image quality for a specific data rate. The conversion of video data is not a legal problem, as long as it is not redistributed, say, over the Internet. Passionate video makers are another group that continually discusses the efficient MPEG-4 compression standard. Owners of modern DV cameras (DV video with 3.6 MB/s) can transfer vacation videos directly from the camera to the PC and continue to edit them from there. After a film project has been rendered, it is possible to save the desired sequence in MPEG-4 format with full PAL resolution (720 x 576 dots). Friends and acquaintances will be amazed when they suddenly see an entire vacation movie saved on a single CD-ROM. That means up to 65 minutes of movie in stereo together with high image quality!
Flask 4.1 after start-up.
Flask 4.1, under the name «Xmpeg».
The New Flask 4.1/DivX 4.01 Codec, Continued
«Components» of the new Flask 4.1.
The most frequently used tool for making MPEG-4 files is Flask Mpeg. The software, available on the Internet as freeware, relies on the MPEG-4 Codec «DivX» — which is a trademark of DivXNetworks, Inc — in which parameters, settings, and special CPU register settings are transferred.
The programmers succeeded in making significant advances with the new Flask 4.1 version, which is now also called Xmeg. We tested the most current version together with the DivX-4.01-codec, which is also new. All software can be downloaded at DivXVIDEO. First and foremost, we can confirm that Flask 4.1 has become considerably more stable than past versions — there are fewer sudden program crashes.
The convenient menu selection, which now has features that are almost professional, deserves special mention. However, we discovered several weak points that allow sufficient room for improvement.
The THG-CPU video was converted to MPEG-4 format with Flask 4.1.
A look at the settings: Flask 4.1 displays all available functions.
Flask 4.1: The special instruction sets of modern CPUs are used and supported for faster MPEG-4-encoding.
Source: DVD Film or MPEG-2 Video
A wealth of languages: Flask 4.1 can be used almost anywhere in the world.
Selecting the output format: AVI for MPEG-4 or MPEG-1 or MPEG-2 via the bbMPEG encoder.
In principle, this latest version of Flask Mpeg processes the same video formats as the earlier versions: VOB files can be read directly from DVD-ROM or MPEG-2 videos. The DVD-ROM option is available when a complete film is to be converted from a DVD into MPEG-4 format. MPEG-2 files can also be edited as desired. One peculiarity must be noted when copying DVD videos: Flask 4.1 needs the *.IFO script file so that the individual VOB files can be recognized on a DVD as a complete movie. Otherwise it is necessary to laboriously code each VOB file (about 20 minutes of film) individually and then link them together. With conventional MPEG videos everything is much easier. Both the video and audio streams are recognized and Flask transfers the desired parameters to the DivX Codec (MPEG 4 codec).
Source: DVD Film or MPEG-2 Video, Continued
Video and audio settings can be entered via the «Output format options» menu.
The «Output format options» menu after running Flask 4.1 for the first time. No codecs have been selected yet.
Selecting video and audio codecs.
Concentrated PC Power Needed!
Support for CPU instruction sets like SSE2 or 3Dnow.
High-speed encoding with SSE2 expansion. However, only Intel Pentium 4 currently supports this instruction set.
We cannot stress this enough: to convert or create MPEG-4 files, a huge amount of CPU power is necessary. Otherwise encoding a single movie can take several days! For example: we often use an Intel Pentium 4/2000 clocked to 2300 MHz for MPEG-4 encoding, together with 512 MB of RAM and a fast Ultra-160-SCSI hard drive. That means that for full PAL resolution (720 x 576 dots) and sound with 128 KBit/s at 44 kHz, a frame rate of only about 19 images per second is reached, and the results should be similar for NTSC encoding too. However, we use the best iDCT mode, cut out the black frame and select the most efficient compression method in such a way that the processor load is increased by up to 50 percent. Flask 4.1 supports both the SSE2 expansions of the Pentium 4 processors and the 3Dnow instructions of the AMD Athlon CPUs. Even the new Athlon XP with its SSE expansions is supported, although, when it comes to MPEG encoding, the AMD CPUs generally pale in comparison to the Intel processors.
Data Press: 735 MB For 65 Minutes Of Video
The «Global project options» menu contains all settings needed to output the video.
Our laboratory tests showed that standard blank CDs with a capacity of 700 MB (CD-R 80) can be stretched by overburning to up to 735 MB. This makes it possible to put about 65 minutes of video from a DVD-ROM at full PAL or NTSC resolution and stereo sound with 128 KBit/s. If you want to save a longer film sequence on a single CD-R, you can either lower the resolution (to about 640×480 dots), or decrease the data rate. To do this we experimented with various MPEG-4 codecs and settings, although the DivX 3.20a codec can still be considered the best. Even the new DivX 4.01 codec, despite its many adjustment options, does not reach the image quality of the DivX 3.20a codec. The codec 3.20a is misleadingly being offered as the 3.2.
Only complete PAL or NTSC resolutions makes sense. Gone are the days when videos were the size of postage stamps.
The NTSC standard used in the US calls for 30 frames per second. 25 frames per second should only be selected for PAL films.
A Tough Choice: DivX 3.20a Codec Still Better Than DivX 4.01 Codec
The old DivX 3.20a codec still offers the best video quality.
Limited options for settings with DivX 3.20a codec.
Before starting to encode a movie, the optimum video and audio data rate should be set. Make no compromises on the video resolution: Full PAL or NTSC resolution is a must. Finally, the days of wobbly sequences in postage-stamp size are over. A good balance between video quality and data rate at full PAL or NTSC resolutions can be achieved if the video data stream is set at a maximum of 1500 KBit/s. For the DivX 3.20a codec this means that at 187.5 KB/s of video, about 67 minutes fit on a CD-ROM — although still without an audio signal. With an audio portion (data flow audio+video at 203.5 KB/s), assuming a constant data rate, about 62 minutes of high-quality film fit on a CD with 735 MB of capacity. Skimping on the data rate of the audio signal is also not advisable. Stereo sound with 128 KBit/s at a 44.1 kHz sample rate provide sound that is comparable with that of an audio CD.
A Tough Choice: DivX 3.20a Codec Still Better Than DivX 4.01 Codec, Continued
The new DivX 4.01 codec.
A wide variety of adjustment options with the DivX 4.01 codec.
We’ve arrived at the two best DivX codecs: The new DivX Version 4.01 has more options for settings available, while the earlier DivX 3.20a only allows the maximum data rate to be adjusted. The DivX 3.20a codec also let you set the focus and the number of key frames. On the other hand, the DivX 4.01 codec has considerably more to offer. First off, one can choose between various methods for the variable bit rate. Also, the precision of the DCT can be freely selected using the «Performance/Quality» option. The «Deinterlace» option produces a more homogeneous image — especially with difficult scene transitions. The option for setting Flask’s CPU load by percentages is also completely new. That is totally different with DivX 3.20a codec: This codec reserves the maximum CPU load for itself. For die-hard MPEG freaks who want to optimize the encoding down to the very last bit, DivX 4.01 codec offers the option of manually setting all encoding parameters. However, the image quality attainable always depends on the complexity and the number of motion vectors within a video sequence. In a lab test we found that the DivX 4.01 codec, despite its numerous setting options, does not quite equal the image quality of the earlier DivX 3.20a codec. It bears mentioning that this was at the same data rate — we have always worked with a video bit rate of 1500 KBit/s in order to get a reasonable result at full PAL resolution in our European labs.
Fine Adjustments: Resolution, Detail And Filter
The «BiCubic» filter gave us the best video quality in our tests.
Selecting the right portion of the image using the detail window.
As most films available on DVD are in broadband (cinema) format, a fine adjustment of the resolution is advisable. In concrete terms, this means that only the areas containing image information are actually coded. Otherwise the black edges (which are required as part of the 16:9 format) get coded in the MPEG-4 format as well, so that in the worst possible case, the data stream increases by up to 15 percent. Filtering is a topic that deserves its own chapter. According to our findings, «BiCubic» produces the best results with Flask 4.1.
The converted video is saved in this directory on the hard drive.
Format Ratio: 16:9 or 4:3
The width-height ratio can also be adjusted manually.
Encoding resolution — visible in the top left corner of the video window.
There are several films on DVD whose format ratio is not recognized by Flask. The result is a distorted image when viewed on the player that can only be eliminated manually. To do this, a setting of «4:3» or «16:9» must be selected in the «Post Processing» menu.
Detail of the black bar in the 16:9 cinema format.
Standard setting with no adjustment to the encoding frame.
Post-Processing: Brightness And Volume
Super feature: Increasing brightness by 25 percent will produce a perfect video image.
Louder: In the past, most movies were way too quiet after encoding. This feature helps increase the volume by 180 percent.
The two most useful features of Flask 4.1 have to do with image brightness and volume of the audio signal. Many users are familiar with the problem that came up in earlier Flask versions: after MPEG-4 encoding, the image in the finished video was too dim. In previous versions, Flask did not allow for correcting this, but the new Flask now comes equipped with this feature.
We have determined that an increase in brightness of 25 percent produces the best possible image. A similar thing occurs with the sound signal: most videos were so quiet that we had to set them to maximum volume during playback. Flask 4.1 allows the volume to be raised by percentages via a special menu. We worked with the «180 percent» setting, which produced an ideal volume when the MPEG-4 film was completely coded.
Summary: DivX 4.01 Codec Not Yet Perfect — Flask 4.1 Is The Best Version
The new Flask 4.1 shows significant progress and improvement over previous versions. It allows the adjustment of image brightness as well as the audio volume. Of primary importance is the high degree of user-friendliness, with clear graphic menus, along with the fact that all settings can be saved individually.
Flask 4.1 supports all of the latest processors, including Intel Pentium 4 and AMD Athlon XP/MP. Special instruction sets like SSE2 or 3Dnow, which provide in any case for a noticeable increase in speed in MPEG-4 encoding, are automatically recognized. With an Intel Pentium 4/2000 using the standard settings (in our example, full PAL resolution with 720 x 576 dots, stereo audio signal with 128 KBit/s and 44.1 kHz sample rate), for example, an average frame rate of about 20 frames per second (fps) can be reached during encoding. The use of special functions to improve image quality increases the workload on the computer so much that the frame rate can quickly drop to 14-15 fps.
Encoding errors that occurred with DivX 4.01 codec.
We were not entirely satisfied with the DivX 4.01 codec, which offers numerous features for optimized encoding. What counts ultimately is the image quality of the video that is output at the end and the proportional data rate. This happens to be the selling point for the «older» DivX 3.20a codec — for example, at a video data rate of 1500 KBit/s, a high-quality video with full PAL or NTSC resolution is possible. If you test the individual features of the DivX 4.01 codec, assuming the same data rate, the result is a lower-quality image. These findings, however, are purely subjective and it is entirely possible that they will vary depending on image content.
Flask 4.1 in action.
