derive codec from file extension for remotion lambda

packages/cli/src/get-cli-options.ts

@@ -34,9 +34,9 @@ const getFinalCodec = async (options: {isLambda: boolean}) => {
 
 	const codec = getFinalOutputCodec({
 		codec: userCodec,
-		fileExtension: options.isLambda
-			? null
-			: RenderInternals.getExtensionOfFilename(getUserPassedOutputLocation()),
+		fileExtension: RenderInternals.getExtensionOfFilename(
+			getUserPassedOutputLocation()
+		),
 		emitWarning: true,
 	});
 	const ffmpegExecutable = ConfigInternals.getCustomFfmpegExecutable();

packages/lambda/src/api/render-media-on-lambda.ts

@@ -6,6 +6,7 @@ import type {
 	PixelFormat,
 	ProResProfile,
 } from '@remotion/renderer';
+import {RenderInternals, validateOutputFilename} from '@remotion/renderer';
 import {VERSION} from 'remotion/version';
 import type {AwsRegion} from '../pricing/aws-regions';
 import {callLambda} from '../shared/call-lambda';
@@ -111,6 +112,13 @@ export const renderMediaOnLambda = async ({
 		durationInFrames: 1,
 	});
 	validateDownloadBehavior(downloadBehavior);
+	if (outName === undefined || typeof outName === 'string') {
+		validateOutputFilename(
+			codec,
+			RenderInternals.getExtensionOfFilename(outName ?? null)
+		);
+	}
+
 	const realServeUrl = await convertToServeUrl(serveUrl, region);
 	try {
 		const res = await callLambda({

packages/lambda/src/cli/commands/still.ts

@@ -49,7 +49,7 @@ export const stillCommand = async (args: string[]) => {
 	const {
 		chromiumOptions,
 		envVariables,
-		imageFormat,
+		imageFormat: cliImageFormat,
 		inputProps,
 		logLevel,
 		puppeteerTimeout,
@@ -69,6 +69,40 @@ export const stillCommand = async (args: string[]) => {
 	const privacy = parsedLambdaCli.privacy ?? DEFAULT_OUTPUT_PRIVACY;
 	validatePrivacy(privacy);
 
+	let imageFormat = cliImageFormat;
+
+	if (outName) {
+		if (cliImageFormat === 'none') {
+			if (outName?.endsWith('.jpeg') || outName?.endsWith('.jpg')) {
+				Log.verbose(
+					'Output file has a JPEG extension, setting the image format to JPEG.'
+				);
+				imageFormat = 'jpeg';
+			}
+
+			if (outName?.endsWith('.png')) {
+				Log.verbose(
+					'Output file has a PNG extension, setting the image format to PNG.'
+				);
+				imageFormat = 'png';
+			}
+		}
+
+		if (imageFormat === 'png' && outName.endsWith('.png')) {
+			Log.warn(`Rendering a PNG, expected a .png extension but got ${outName}`);
+		}
+
+		if (
+			imageFormat === 'jpeg' &&
+			!outName.endsWith('.jpg') &&
+			!outName.endsWith('.jpeg')
+		) {
+			Log.warn(
+				`Rendering a JPEG, expected a .jpg or .jpeg extension but got ${outName}`
+			);
+		}
+	}
+
 	try {
 		const res = await renderStillOnLambda({
 			functionName,

packages/renderer/src/index.ts

@@ -103,6 +103,7 @@ export {StitcherOptions, stitchFramesToVideo} from './stitch-frames-to-video';
 export {SymbolicatedStackFrame} from './symbolicate-stacktrace';
 export {OnStartData, RenderFramesOutput} from './types';
 export {OpenGlRenderer} from './validate-opengl-renderer';
+export {validateOutputFilename} from './validate-output-filename';
 export const RenderInternals = {
 	ensureLocalBrowser,
 	ffmpegHasFeature,