--- id: "en/preview-transcoding" title: "Preview and transcoding" language: "en" description: "Preview formats, optional modules, BabelViewer capabilities and private-deployment transcoding." canonical_url: "https://www.babel.cc/public/babelwiki/en/preview-transcoding.html" markdown_url: "https://www.babel.cc/public/babelwiki/ai/en/preview-transcoding.md" alternates: {"en": "https://www.babel.cc/public/babelwiki/ai/en/preview-transcoding.md", "zh": "https://www.babel.cc/public/babelwiki/ai/zh/preview-transcoding.md"} reading_note: "文档记录不等于当前部署能力；以实际版本、授权模块与配置为准。保留原文的可选、限制及待确认说明，勿补猜接口。 / Documentation is not a guarantee for every deployment. Preserve optional-module requirements, limitations and unresolved API contracts." --- # Preview and transcoding BabelBird uses previewers and server-side conversion to provide online file previews. Users can view previews without downloading the original file; this does not mean that photography, screenshots or other forms of content copying can be prevented. ## File types supported for online preview The following is the product-provided preview support list. Optional capabilities require the corresponding server modules. All formats supported for preview support BabelViewer annotations except Excel and audio/video; optional formats require their preview modules to be enabled first. Preview and annotation support do not establish online editing support. All files that can be previewed in a flat, two-dimensional view are within PDF conversion scope, except audio/video and 3D; the required preview and conversion modules must be enabled. Encoding, file content and modules affect whether a particular file opens successfully. | Type | Base support | Optional support and conditions | | --- | --- | --- | | Text, code, Office and documents | pdf, md, js, xml, htm, html, css, scss, jsp, c, cpp, java, php, m, h, hpp, mm, mail, msg, epub, doc, docx, ppt, pptx, xls, xlsx, txt, rtf, wps, wpt, dps, dpt, et, ett | key, numbers, pages; requires a server module | | Mind maps | xmind, km | — | | Audio and video | mp3, mp4, wav, asf, ape | flv, f4v, m4v, webm, 3gp, 3gpp, wmv, avi, rm, rmvb, mkv, mov, mpeg, swf, mpg, mts, m2ts, ogv | | 3D | dae, 3ds, abc, fbx, mtl, obj, ply, stl, x3d | Optional module one: m3d; Revit, SOLIDWORKS and 3ds Max files from all versions through 2026 require purchase of the corresponding 3D transcoding service; see extensions below | | Images | bmp, jpg, jpeg, gif, png, psd, tif, tiff, raw, cr2, arw, dng, nef, pef, dcm, ico | — | | Medical images | dicom | — | | Vector and design files | ai, svg, eps, indd, indt, idml | — | | CAD | dwg, dwt, dxf, dcm | — | | Archives | — | rar, zip | Formats already covered by base modules have been removed from the optional lists; MP4, ASF, X3D, PLY, 3DS and ABC remain in the base lists. Audio/video browser and codec compatibility primarily follows DPlayer playback support; an extension alone does not guarantee successful playback. The product format list places dcm under both images and CAD. Both entries are retained; the extension alone is not used here to distinguish their content. ## BabelViewer preview and collaboration Built on HTML5, BabelViewer combines multiple rendering libraries for different file types and uses multiple layers for collaborative drawing and online annotation discussions. - View annotation lists for current and historical versions. - Compare versions of multiple file types and switch quickly between files. - Magnify vector content at high zoom levels. - Render 3D content with WebGL and provide 3D annotations. All preview-supported formats except Excel and audio/video support BabelViewer annotations; this does not mean every format offers identical drawing, comparison or text-selection tools. BabelBird’s deeply customized ONLYOFFICE provides Office online editing, Office comments and PDF conversion as a separate component from BabelViewer. Excel does not support BabelViewer annotations but does support cell comments in ONLYOFFICE; available entry points depend on modules and permissions. See [Online editing](https://www.babel.cc/public/babelwiki/en/online-editing.html), [Preview, annotations and review](https://www.babel.cc/public/babelwiki/en/preview-annotation-review.html) and [Automatic PDF conversion](https://www.babel.cc/public/babelwiki/en/automation-pdf.html). ## Transcoding in private deployments Private deployments can use dedicated servers or virtual machines for transcoding, with multiple conversion tools generating preview content and thumbnails. 1. When the system is idle, files can be pre-converted after upload to reduce waiting when previews are opened later. 2. During busy periods or bulk uploads, pre-conversion can be deferred. Files opened for preview receive priority in the queue for on-demand conversion. 3. An asynchronous queue processes conversion tasks. Generated preview caches can be reused, and multiple processing nodes can balance the load. Queue priority does not mean immediate completion. Waiting time depends on file content, queued tasks and processing resources. This information does not specify busy-state thresholds, concurrency limits or cache retention policies and cannot establish a fixed completion time. ## When a file will not preview Confirm that upload has completed and the current account has access, then check the extension, file integrity and deployment of any required optional module. Files requiring conversion may still be queued or processing. Preserve the original and record the error, file type and client or browser version so an administrator can check conversion tasks and modules. Preview failure alone does not prove that the original file is damaged. See [Preview and search FAQ](https://www.babel.cc/public/babelwiki/en/faq-preview-search.html) and [Annotation and preview troubleshooting FAQ](https://www.babel.cc/public/babelwiki/en/faq-archive-annotation.html). ## Native extensions for professional 3D files The Revit, SOLIDWORKS and 3ds Max transcoding services support files from all versions through 2026. The corresponding 3D transcoding service must be purchased separately. The native extensions below are based on vendor documentation to help identify files. Include resources referenced by the model and check the conversion result during deployment. | Product | Native extensions and purpose | Official reference | | --- | --- | --- | | Revit | RVT project, RFA family, RTE project template, RFT family template | [Revit file types](https://www.autodesk.com/support/technical/article/caas/sfdcarticles/sfdcarticles/Revit-file-types.html) | | SOLIDWORKS | SLDPRT part, SLDASM assembly, SLDDRW drawing | [SOLIDWORKS file types](https://help.solidworks.com/2020/English/SolidWorks/acadhelp/c_Types_of_Files.htm) | | 3ds Max | MAX scene | [MAX files](https://help.autodesk.com/cloudhelp/2022/ENU/3DSMax-Reference/files/GUID-88DE2443-6869-4820-973A-10E7695B6DE6.htm) | ## Audio/video playback and DPlayer Audio/video browser and codec compatibility primarily follows DPlayer playback support. Normal playback relies on browser HTML5 media capabilities. HLS, DASH and FLV paths also depend on the corresponding adapters, such as hls.js, dash.js/Shaka and flv.js, and browser codec/MSE support. Check which paths are enabled in the BabelBird deployment rather than assuming every upstream option is enabled. DPlayer is a playback component, not a replacement for server-side transcoding. See [DPlayer playback and MSE support](https://dplayer.diygod.dev/guide#mse-support). ## Flat previews and PDF conversion All files that can be previewed in a flat, two-dimensional view are within PDF conversion scope, excluding audio/video and 3D. BabelBird’s customized ONLYOFFICE provides the corresponding Office conversion capabilities; images, CAD and other types use their respective conversion tools. Required modules must be enabled. Viewing an archive’s directory listing does not mean that the whole archive can be converted to PDF; assess the individual files inside it for flat-preview support. See [Automatic PDF conversion](https://www.babel.cc/public/babelwiki/en/automation-pdf.html).