Unfamiliar encoding of string (Base64?) - Trying to save and use string contents of .3gp file

Question

I'm attempting to read the contents of a .3gp file as a string to later save that string as a valid .3gp file once again.

When I read the string contents, it seems to be differently encoded than when I look at the string contents of a .3gp file on Windows.

Here is an excerpt from the beginning of the string contents I received:

\u0000\u0000\u0000\u0018ftyp3gp4\u0000\u0000\u0000\u0000isom3gp4\u0000\u0000\t�moov\u0000\u0000\u0000lmvhd\u0000\u0000\u0000\u0000�o�K�o�K\u0000\u0000\u0003�\u0000\u0000 �\u0000\u0001\u0000\u0000\u0001\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0001\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0001\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000@\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0002\u0000\u0000\u0000�meta\u0000\u0000\u0000!hdlr\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000mdta\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000dkeys\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0003\u0000\u0000\u0000\u001bmdtacom.android.version\u0000\u0000\u0000 mdtacom.android.manufacturer\u0000\u0000\u0000\u0019mdtacom.android.model\u0000\u0000\u0000`ilst\u0000\u0000\u0000\u001d\u0000\u0000\u0000\u0001\u0000\u0000\u0000\u0015data\u0000\u0000\u0000\u0001\u0000\u0000\u0000\u00008.1.0\u0000\u0000\u0000\u001e\u0000\u0000\u0000\u0002\u0000\u0000\u0000\u0016data\u0000\u0000\u0000\u0001\u0000\u0000\u0000\u0000Google\u0000\u0000\u0000\u001d\u0000\u0000\u0000\u0003\u0000\u0000\u0000\u0015data\u0000\u0000\u0000\u0001\u0000\u0000\u0000\u0000Pixel\u0000\u0000\b1trak\u0000\u0000\u0000\tkhd\u0000\u0000\u0000\u0007�o�K�o�K\u0000\u0000\u0000\u0001\u0000\u0000\u0000\u0000\u0000\u0000

A valid .3gp file's contents when opened in Notepad on Windows look like the following excerpt shows:

ftyp3gp4 isomiso23gp4 free -kmdat<§!4ˆÉ‡€èÕ_ÒA@€ vÞm¾ ©°Ï@; €$::=>zá!3³³Ó×ùžŸ8HLììøýÂBg‡‡çî<f¦§QÓ3366sŽ™™‘©£œtÌLÌ#f\bé2ÒÂòçXÉ••–:ÅÌ œ¬¥Ú.däÅ$îñS%$&%w‰š|„ÐѤ&€‚ˆŠÝ#4TVé  £#7ÈÍ ºFˆGУ#7ÈÄ„}¾Fh((ˆò2 ¡ *Šïšy¾AÉùñí*W…ÿŠ£MÛJ…È»4ò\ÇÃú£×©ÎC—‰ñôŸü™Iœž(²z™¦ÿå;õÕ®]ÁB>ªÇŠGma,H(â > tNÊvt~b$ _W¿¢4•¶Ñ9Ñ_â©¥„ñž—÷ ¡æñ¹ ͨéZç£JmdÁ÷•ƒ_sÊvîü¾òµÉÒ̃S±,yðÆ4¼?ü0MU†ÝKÞ £ÏÊÑ#£n1t”ØâX<Oã£ïBAx!—O²×ÈáÄ’àB/¾a¿LÔÐàÝÊ:f†fÆÎqÓ1043s™yq‘‹¤dËJËËc&VRZXë2‚r¢—h©¢£%%7IJŽŽ––}¶J4„ƒé‰²SHIMMm’‰$úJjkd•O¥MMm’šRJjklœÒRSS[dãHG>˜–Ý$ÝÈ-ò¥jýš§;‡’ÎBýT+Un[uÎÁAøn(HÀCñöÈBOǪÆ'@–¨ºAÜØ|qí½"yOÕ]1¨ò¿cm €<IT%´¡$h I/@ô˜Õ4‘@èõI– BŠtóÊÇʽoAË}PÊ’ž!/.QퟪóÍæjF@ÀzP>@B®—ùUôùbi%VýVüw»ÞÓÎ àñ^{s$t~/ÕÕj•+ËTU{k“¦ÏNÕ
ËÇíE°2->ú¸\¬w?ù¸:“‰NÏt‰’XÇIP5f‰P^€9TT%LªTŽÆ°ÁXôKþÌÁÖLìé ùÆ>g'§Ž1ó65:9rŽ™¡™¹«œtÌL #&^\bé2ÂÂâçXÈ“O¦¨(¶IQ8úyõ%6¹J(P>¦¦×'…ê'ÕOµÉõê'ÕOªŸj”ê'ÔOªŸU>×)ÔO¨ŸU>ª}®N5ꪒsPNTSl“šrjš‹d›4ĵì‹:Kjïf–”žœâ•›ÈÕ‚Ÿè^òÀÕU kËâ§Ù|lœ€Á°aÿ|0ÇõPþ7s÷ÕE6zHä'•ÕûiǔŠ£œÒ¿Úó}TªP­²tÅ}|A‹çøª¢‡Â ü¹GUÉSÜ{TH¯|y'Æ’A€ ÷à‘».Óp€ÀyßQ&,³#K™• û|ŒÐÑ›äfzv€~á!3£ƒÓ·ù›šœœ9GÌÐÌØÙÎ6f&†n‘³TUWYk“šª²ÒÓT¥•Ï«Ÿ[>¸Õ)Eƒë×Zef²²ººÕ)5••ÕÖ©I¬¬®®µJÑdú¹õÕ¶¹Z+ŸV>¶¶×'Ecê§Ö–Zå,¨}LúÁõ†ÉI©©

I believe the type of string I've received is Base64 based on some searches I did, and I've noticed processing the string in javascript with unescape(encodeURIComponent()) gives me a somewhat similar result to the valid .3gp contents, but it's not exact.

Does anyone know what I need to do to the string to make it look like the valid .3gp file string contents in Windows? Is this even possible at all?

Answer 1

Since you only need to be able to download it, holding it as a string is fine. If you can use a Node Buffer instead, it will be a bit more robust, but javascript string should carry all of your bytes through.

Be careful how you handle the download api to make sure it doesn't get turned into something else.