How to add a fallback adaptation set to mpeg-dash manifest using ffmpeg and dash.js?

Question

I have previously successfully made mpeg-dash manifests using the following ffmpeg command:

ffmpeg -i input.webm -c:v copy -c:a copy -f dash -seg_duration 15 manifest.mpd

Where input.webm is a VP9 and opus encoded video file, so no re-encoding is needed. Therefore I just copy both streams.

Now I am trying to add an adaption set to this manifest for those devices that do not support VP9 and/or opus, using the following command (linebreaks added for legibility):

ffmpeg -i input.webm 
-map 0:v:0 -map 0:a:0 -map 0:v:0 -map 0:a:0 
-c:v:0 copy 
-c:a:0 copy 
-c:v:1 libx264 -b:v:1 1000k 
-c:a:1 aac -b:a:1 128k
-adaptation_sets "id=0,streams=v id=1,streams=a" -f dash -seg_duration 15 manifest.mpd

ffmpeg seems to agree with me and spits out what I would expect, namely the same files as in the previous command and additional files that resemble something like mp4 and aac chunks. But my website with dash.js does not accept this manifest, the video does no longer play. Also dash.js does not produce any errors in the browser console. What did I do wrong?

manifest:

<?xml version="1.0" encoding="utf-8"?>
<MPD xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="urn:mpeg:dash:schema:mpd:2011"
    xmlns:xlink="http://www.w3.org/1999/xlink"
    xsi:schemaLocation="urn:mpeg:DASH:schema:MPD:2011 http://standards.iso.org/ittf/PubliclyAvailableStandards/MPEG-DASH_schema_files/DASH-MPD.xsd"
    profiles="urn:mpeg:dash:profile:isoff-live:2011"
    type="static"
    mediaPresentationDuration="PT46.7S"
    maxSegmentDuration="PT15.0S"
    minBufferTime="PT40.0S">
    <ProgramInformation>
    </ProgramInformation>
    <ServiceDescription id="0">
    </ServiceDescription>
    <Period id="0" start="PT0.0S">
        <AdaptationSet id="0" contentType="video" startWithSAP="1" segmentAlignment="true" bitstreamSwitching="true" frameRate="25/1" maxWidth="1920" maxHeight="1080" par="16:9">
            <Representation id="0" mimeType="video/webm" codecs="vp09.00.40.08" bandwidth="713" width="1920" height="1080" scanType="unknown" sar="1:1">
                <SegmentTemplate timescale="1000" initialization="init-stream$RepresentationID$.webm" media="chunk-stream$RepresentationID$-$Number%05d$.webm" startNumber="1">
                    <SegmentTimeline>
                        <S t="92" d="19200" r="1" />
                        <S d="8320" />
                    </SegmentTimeline>
                </SegmentTemplate>
            </Representation>
            <Representation id="2" mimeType="video/mp4" codecs="avc1.640028" bandwidth="1000000" width="1920" height="1080" sar="1:1">
                <SegmentTemplate timescale="12800" initialization="init-stream$RepresentationID$.m4s" media="chunk-stream$RepresentationID$-$Number%05d$.m4s" startNumber="1">
                    <SegmentTimeline>
                        <S t="1024" d="244736" />
                        <S d="256000" />
                        <S d="97280" />
                    </SegmentTimeline>
                </SegmentTemplate>
            </Representation>
        </AdaptationSet>
        <AdaptationSet id="1" contentType="audio" startWithSAP="1" segmentAlignment="true" bitstreamSwitching="true">
            <Representation id="1" mimeType="audio/webm" codecs="opus" bandwidth="96" audioSamplingRate="48000">
                <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
                <SegmentTemplate timescale="1000" initialization="init-stream$RepresentationID$.webm" media="chunk-stream$RepresentationID$-$Number%05d$.webm" startNumber="1">
                    <SegmentTimeline>
                        <S t="80" d="15001" />
                        <S d="15000" r="1" />
                        <S d="1757" />
                    </SegmentTimeline>
                </SegmentTemplate>
            </Representation>
            <Representation id="3" mimeType="audio/mp4" codecs="mp4a.40.2" bandwidth="128000" audioSamplingRate="48000">
                <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2" />
                <SegmentTemplate timescale="48000" initialization="init-stream$RepresentationID$.m4s" media="chunk-stream$RepresentationID$-$Number%05d$.m4s" startNumber="1">
                    <SegmentTimeline>
                        <S t="3152" d="720920" />
                        <S d="720896" r="1" />
                        <S d="81920" />
                    </SegmentTimeline>
                </SegmentTemplate>
            </Representation>
        </AdaptationSet>
    </Period>
</MPD>

Answer 1

An AdaptationSet must contain the bitrate variant streams (Representations) for one codec only. In the example MPD you've posted, the video adaptation set contains variants for both your VP9 and H.264 video streams.

(This is because when you use the id=0,streams=v syntax in FFMPEG, it will put all of your video streams into one adaptation set.)

I haven't tested it, but changing the last line of your ffmpeg command to something like this should get each codec in its own adaptation set:

-adaptation_sets "id=0,streams=0 id=1,streams=1 id=2,streams=2 id=3,streams=3" -f dash -seg_duration 15 manifest.mpd