[{"data":1,"prerenderedAt":222},["ShallowReactive",2],{"guide-en-check-a-file-that-will-not-play":3,"guide-en-check-a-file-that-will-not-play-related":219},{"id":4,"title":5,"author":6,"body":7,"date":204,"description":205,"difficulty":206,"extension":207,"image":208,"lastModified":204,"meta":209,"navigation":210,"outcome":211,"path":212,"readingTime":213,"robots":208,"scenario":214,"seo":215,"stem":216,"tools":217,"__hash__":218},"guides\u002F8.guides\u002F3.check-a-file-that-will-not-play.md","Why a File That Won't Play Is Usually Two Problems","FlowPick Team",{"type":8,"value":9,"toc":194},"minimark",[10,14,19,22,30,36,39,46,52,55,58,62,71,77,82,85,113,116,120,128,136,142,147,151,154,157,160,163,167,179,183,186],[11,12,13],"p",{},"Someone sends you a video. It will not open. The instinct is to convert it to MP4. Half the time that fixes it, and half the time you spend twenty minutes converting a file whose real problem was never the container.",[15,16,18],"h2",{"id":17},"two-problems-that-look-identical","Two problems that look identical",[11,20,21],{},"A media file has two layers that matter here.",[11,23,24,25,29],{},"The ",[26,27,28],"strong",{},"container"," is the box: MP4, WebM, MKV, TS, MOV. It says where the streams live, not what they are. Each format is a published specification — MP4 is standardised as ISO\u002FIEC 14496-12, Matroska and WebM have their own.",[11,31,24,32,35],{},[26,33,34],{},"codec"," is what is inside: H.264, H.265, VP9, AV1 for video; AAC, Opus, AC-3 for audio.",[11,37,38],{},"A player that cannot open a file is usually reporting a container problem, because it cannot even find the streams to try decoding them. But a player that opens the file and then shows a black frame or silent audio has a codec problem, and no amount of container swapping will help.",[11,40,41],{},[42,43],"img",{"alt":44,"src":45},"Comparing containers and codecs: MKV and MP4 holding the same H.264 and AAC streams can be remuxed, while an MP4 holding H.265 needs a re-encode","\u002Fimg\u002Fguides\u002Fcontainer-vs-codec.svg",[11,47,48],{},[49,50,51],"em",{},"Changing the box is cheap and lossless. Changing what is inside is neither.",[11,53,54],{},"Converting the container is called remuxing. It copies the encoded streams into a new box. It is fast, it needs no quality loss, and it is the right answer when the box is the problem.",[11,56,57],{},"Re-encoding decodes every frame and compresses it again. It is slow, it loses a little quality, and it is the only answer when the codec is the problem.",[15,59,61],{"id":60},"step-1-read-the-file-instead-of-guessing","Step 1: Read the file instead of guessing",[11,63,64,65,70],{},"Drop the file into ",[66,67,69],"a",{"href":68},"\u002Ftools\u002Fvideo-info","Video Info",". It reports the container, the video and audio codecs, resolution, duration and track layout.",[11,72,73],{},[42,74],{"alt":75,"src":76},"Media report showing MP4 container, four-second duration, AVC video and AAC audio tracks","\u002Fimg\u002Fguides\u002Fvideo-info-output.jpg",[11,78,79],{},[49,80,81],{},"Generated four-second MP4 with AVC\u002FH.264 video and AAC audio. Unavailable bitrate fields are shown honestly rather than estimated.",[11,83,84],{},"What you are looking for:",[86,87,88,95,101,107],"ul",{},[89,90,91,94],"li",{},[26,92,93],{},"Container is MKV or TS, codecs are H.264 + AAC."," Your player simply does not handle the box. Remux to MP4 and you are done in a minute or two.",[89,96,97,100],{},[26,98,99],{},"Container is MP4, video codec is H.265."," The box is fine; the player lacks an H.265 decoder. Remuxing will not help. You need an actual re-encode to a codec your player supports. The WebM converter targets WebM input; for an H.265 MP4, use an encoder that supports that source format.",[89,102,103,106],{},[26,104,105],{},"Audio codec is AC-3 or DTS."," Common in files ripped from discs. Some browsers and phones will not play them even in an MP4 container. The fix is re-encoding the audio, not the video.",[89,108,109,112],{},[26,110,111],{},"No audio track at all."," Not a format problem. The recording was silent.",[11,114,115],{},"That last case catches people regularly: a \"broken video\" that simply has no sound because the capture tool did not record any.",[15,117,119],{"id":118},"step-2-choose-between-remuxing-and-re-encoding","Step 2: Choose between remuxing and re-encoding",[11,121,122,123,127],{},"For a TS file containing compatible H.264 video and AAC audio, use ",[66,124,126],{"href":125},"\u002Ftools\u002Fts-to-mp4","TS to MP4",". It copies the encoded streams into MP4 without re-encoding. The file may become smaller because the new container has different overhead.",[11,129,130,131,135],{},"For a browser recording in WebM, use ",[66,132,134],{"href":133},"\u002Ftools\u002Fwebm-to-mp4","WebM to MP4"," when you need H.264\u002FAAC compatibility. This tool decodes and re-encodes the source; it does not simply swap the container. Conversion takes processing time, may lose some quality, and can increase or decrease file size.",[11,137,138],{},[42,139],{"alt":140,"src":141},"WebM source and MP4 result with different file sizes after re-encoding","\u002Fimg\u002Fguides\u002Fwebm-to-mp4-result.jpg",[11,143,144],{},[49,145,146],{},"WebM conversion is a re-encode, not the TS remux described above. This generated sample grows from 88.9 KB to 122.3 KB.",[15,148,150],{"id":149},"step-3-know-when-to-stop","Step 3: Know when to stop",[11,152,153],{},"There is a category of file this workflow cannot rescue, and recognising it saves an afternoon.",[11,155,156],{},"Encrypted streams are one. If the source was DRM-protected, the segments are ciphertext and there is no container operation that produces playable video.",[11,158,159],{},"Codecs your target device lacks are the other. An H.265 file will not become playable on an H.264-only device by changing its extension or its container. It needs re-encoding, which is a different and slower job.",[11,161,162],{},"Stating it plainly is more useful than a workaround that does not exist: if the file needs a codec the player does not have, the fix is on the player side or in a real encoder.",[15,164,166],{"id":165},"a-note-on-extensions","A note on extensions",[11,168,169,170,174,175,178],{},"Renaming ",[171,172,173],"code",{},"video.webm"," to ",[171,176,177],{},"video.mp4"," does not convert anything. The container is described inside the file, not by its name. Players that trust the extension will fail in confusing ways, and some will refuse the file outright. This is worth mentioning because it is the most common thing people try first.",[15,180,182],{"id":181},"what-you-end-up-with","What you end up with",[11,184,185],{},"Either a file that opens everywhere because the container was the problem, or a clear answer that the codec is the problem and a re-encode is required.",[11,187,188,189,193],{},"For the layers involved — tracks, segments, and why a remux preserves them — the ",[66,190,192],{"href":191},"\u002Fdocs\u002Fadvanced\u002Fdownload-engine","download engine"," page goes deeper.",{"title":195,"searchDepth":196,"depth":196,"links":197},"",2,[198,199,200,201,202,203],{"id":17,"depth":196,"text":18},{"id":60,"depth":196,"text":61},{"id":118,"depth":196,"text":119},{"id":149,"depth":196,"text":150},{"id":165,"depth":196,"text":166},{"id":181,"depth":196,"text":182},"2026-10-29","A container the player does not know and a codec it cannot decode need different fixes. How to read a file, tell the two apart, and when the honest answer is that a re-encode is the only way.","basic","md",null,{},true,"A correct diagnosis, followed by a compatible TS remux, a WebM re-encode, or a clear next step for unsupported codecs.","\u002Fguides\u002Fcheck-a-file-that-will-not-play",6,"convert",{"title":5,"description":205},"8.guides\u002F3.check-a-file-that-will-not-play",[68,133],"uyL5WszuRsBjjgULpELSPR1cP2AGvpmGeaOrW9CJnWA",[220],{"path":212,"title":5,"description":205,"tools":221},[68,133],1793546743906]